Lecture 01
The Skeletal System
Functions of Bones · Classification · General Features of Long Bone · Blood Supply
🦴 Overview
Composed of
Bones, cartilage & ligaments joined tightly → strong, flexible framework for the body
Cartilage
Forms most embryonic/childhood bones; in adults covers joint surfaces
Ligaments
Hold bones together at joints
Tendons
Structurally like ligaments but attach muscle to bone
⚙️ Functions of the Bones
| Function | Description / Example |
|---|---|
| Support | Bones of legs, pelvis & vertebral column hold up the body |
| Protection | Enclose & protect brain, spinal cord, lungs, heart, pelvic organs & bone marrow (e.g. thorax protects heart/lungs, skull protects brain) |
| Movement (Locomotion) | Skeletal muscles attach to bones which act as leverage |
| Blood cell formation (Hemopoiesis) | Red bone marrow is the major producer of blood cells, including most immune cells |
| Electrolyte balance (Mineral storage) | Skeleton = main mineral reservoir — stores & releases calcium & phosphate |
| Triglyceride (Fat) storage | Yellow bone marrow stores triglycerides as a chemical energy reserve |
📐 Classification — According to Position
Axial Bones
Bones forming the head, neck & trunk — skull, vertebral column, thoracic cage (sternum & ribs)
Appendicular Bones
Bones forming the upper & lower limbs
| Part | Upper Limb | Lower Limb |
|---|---|---|
| Girdle | Clavicle & scapula | Hip bone & sacrum |
| Proximal segment | Humerus | Femur |
| Middle segment | Radius & ulna | Tibia & fibula |
| Distal segment | Carpus (8) · Metacarpals (5) · Phalanges (3 each, 2 for thumb) | Tarsus (7) · Metatarsals (5) · Phalanges (3 each, 2 for big toe) |
🔷 Classification — According to Shape
| Type | Description | Example |
|---|---|---|
| Long bones | Longer than wide; act as rigid levers for movement | Humerus, radius, ulna, femur, tibia, fibula, metacarpals/tarsals, phalanges |
| Short bones | Nearly equal in length & width | Carpals (wrist), tarsals (ankle) |
| Flat bones | Enclose/protect soft organs; broad surface for muscle attachment | Most cranial bones, ribs, sternum, scapula |
| Irregular bones | Shape doesn't fit other categories | Vertebrae; sphenoid & ethmoid (skull) |
| Pneumatic bones | Contain air-filled cavities | Frontal, maxilla (skull) |
| Sesamoid bones | Small bones within tendons | Patella (knee cap) |
🧬 Classification — Structure & Development
Compact Bone
Dense, ivory-like — forms the cortex of bones
Cancellous Bone
Spongy-like — lies at ends of long bones, fills most irregular bones
Membranous Development
Intramembranous ossification — bone develops from membrane, e.g. flat bones
Cartilaginous Development
Intracartilaginous (endochondral) ossification — bone develops from cartilage, e.g. long bones
📏 Parts & General Features of a Long Bone
- Diaphysis (Shaft): cylinder of compact bone enclosing the medullary cavity (filled with bone marrow); covered by fibrous membrane periosteum
- Epiphysis (Ends): composed of spongy (cancellous) bone, covered by a layer of hyaline articular cartilage
- Metaphysis: region of the shaft close to the growth cartilage plate
- Epiphyseal growth plate (physis): cartilage between epiphysis & diaphysis in growing bone — site of increase in bone length; ossifies → epiphyseal line
- Nutrient foramina: minute holes through which blood vessels penetrate the bone
Structural layers: Cortex (compact bone) → Medulla (spongy bone + red bone marrow, site of blood cell formation) → Medullary/marrow cavity (yellow bone marrow, fat storage) → Periosteum (covering membrane).
🩸 Blood Supply of the Long Bone
1 · Nutrient Artery
Main supply through the shaft via nutrient foramen
2 · Epiphyseal Artery
Supplies the epiphysis
3 · Metaphyseal Artery
Supplies the metaphysis
4 · Periosteal Artery
Supplies the outer cortex via the periosteum
SKELETAL SYSTEM
⚙️ Functions (6)
Support
Protection
Movement (leverage)
Hemopoiesis (red marrow)
Mineral storage (Ca, PO4)
Fat storage (yellow marrow)
📐 By Position
Axial: skull, vertebral column, thoracic cage
Appendicular: upper + lower limbs
🔷 By Shape (6 types)
Long — femur
Short — carpals
Flat — scapula
Irregular — vertebra
Pneumatic — frontal/maxilla
Sesamoid — patella
🧬 Structure & Development
Compact (cortex) vs Cancellous (spongy)
Intramembranous → flat bones
Intracartilaginous → long bones
🩸 Long Bone Parts & Supply
Diaphysis · Epiphysis · Metaphysis
Growth plate → epiphyseal line
Nutrient · Epiphyseal · Metaphyseal · Periosteal arteries
1
Composition
Skeletal system = bones + cartilage + ligaments. Tendons attach muscle to bone; ligaments attach bone to bone.
2
6 Functions
Support, Protection, Movement, Hemopoiesis, Electrolyte (mineral) balance, Triglyceride storage.
3
Red vs Yellow Marrow
Red marrow → blood cell formation. Yellow marrow → fat/triglyceride storage (energy reserve).
4
Axial vs Appendicular
Axial = head, neck, trunk. Appendicular = upper & lower limbs (girdle + 3 segments each).
5
6 Shapes
Long, Short, Flat, Irregular, Pneumatic, Sesamoid — each with a classic example (femur, carpals, scapula, vertebra, frontal, patella).
6
Compact vs Cancellous
Compact = dense, ivory-like, forms cortex. Cancellous = spongy, at ends of long bones & fills irregular bones.
7
Ossification Types
Intramembranous → flat bones (from membrane). Intracartilaginous → long bones (from cartilage).
8
Long Bone Parts
Diaphysis (shaft) + 2 Epiphyses (ends) + Metaphysis (between). Epiphyses covered by hyaline articular cartilage.
9
Epiphyseal Plate → Line
Growth plate = cartilage that allows lengthening; ossifies at maturity → becomes the epiphyseal line.
10
4 Blood Supplies
Nutrient, Epiphyseal, Metaphyseal, Periosteal arteries — each named for the bone region it supplies.
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TERM
Composition
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Skeletal system = bones + cartilage + ligaments. Tendons attach muscle to bone; ligaments attach bone to bone.
TERM
6 Functions
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Support, Protection, Movement, Hemopoiesis, Electrolyte (mineral) balance, Triglyceride storage.
TERM
Red vs Yellow Marrow
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Red marrow → blood cell formation.
Yellow marrow → fat/triglyceride storage (energy reserve).
Yellow marrow → fat/triglyceride storage (energy reserve).
TERM
Axial vs Appendicular
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Axial = head, neck, trunk.
Appendicular = upper & lower limbs (girdle + 3 segments each).
Appendicular = upper & lower limbs (girdle + 3 segments each).
TERM
6 Shapes
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Long, Short, Flat, Irregular, Pneumatic, Sesamoid — each with a classic example (femur, carpals, scapula, vertebra, frontal, patella).
TERM
Compact vs Cancellous
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Compact = dense, ivory-like, forms cortex.
Cancellous = spongy, at ends of long bones & fills irregular bones.
Cancellous = spongy, at ends of long bones & fills irregular bones.
TERM
Ossification Types
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Intramembranous → flat bones (from membrane).
Intracartilaginous → long bones (from cartilage).
Intracartilaginous → long bones (from cartilage).
TERM
Long Bone Parts
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Diaphysis (shaft) + 2 Epiphyses (ends) + Metaphysis (between). Epiphyses covered by hyaline articular cartilage.
TERM
Epiphyseal Plate → Line
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Growth plate = cartilage that allows lengthening; ossifies at maturity → becomes the epiphyseal line.
TERM
4 Blood Supplies
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Nutrient, Epiphyseal, Metaphyseal, Periosteal arteries — each named for the bone region it supplies.
Lecture 02
The Muscular System
Muscle Types · Construction · Naming · Classification · Action of Muscles
🐭 Origin of the Word "Muscle"
It is the diminutive of the Greek word MUS which means a mouse. The body & head of the mouse represents the belly; the tail represents the tendon.
🔬 Types of Muscle Tissue
| Skeletal | Smooth | Cardiac | |
|---|---|---|---|
| Site / Distribution | Attached to skeleton | In internal viscera & blood vessels | Myocardium (heart wall) |
| Contraction | Voluntary | Involuntary | Involuntary |
| Nerve supply | Somatic | Autonomic | Autonomic |
| Shape | Tubular | Spindle-shaped | Tubular |
| Nucleus | Multinucleated | Single (uninucleate) | Single (uninucleate) |
| Striations | Present | Absent | Present |
| Branching | Not branched | Not branched | Branched & fuse together |
| Fatigability | Fatigues easily | Not easy to fatigue | No fatigability |
🏗️ General Construction of a Skeletal Muscle
- Belly (fleshy belly): the large fleshy portion of the muscle
- Muscle attaches to bone via tendons (cord-like) or aponeuroses (broad & flat); a direct fleshy-to-bone connection is a "fleshy attachment"
- Origin: the more fixed, usually proximal attachment
- Insertion: the more mobile, usually distal attachment — moves towards the origin on contraction, producing joint movement
Connective tissue coverings (the "-mysium" family): Epimysium surrounds the entire muscle · Perimysium surrounds bundles (fascicles) of fibers · Endomysium surrounds individual muscle fibers.
🏷️ Naming of Skeletal Muscles
| Basis | Example | Meaning |
|---|---|---|
| Shape | Deltoid | DELTA = Greek letter D, looks like a triangle |
| Number of origins (heads) | Biceps | BI = two, CEPS = head |
| Size | Adductor magnus | MAGNUS = great, large |
| Length | Adductor longus | LONGUS = long |
| Location | Biceps brachii / Biceps femoris | BRACHII = of the arm; FEMORIS = of the thigh |
| Function | Rotatores | ROTATORES = rotators (turn the vertebral column) |
🧩 Classification — Arrangement of Fibers
- Fibers parallel with the line of pull — e.g. Sartorius
- Pennate fibers (feather-like), oblique to line of pull — uni-, bi-, multipennate (e.g. Extensor digitorum longus / Biceps brachii / Deltoid)
- Oblique, non-pennate fibers — convergent (Pectoralis major) or circular (Orbicularis oris)
- A muscle may have more than one fleshy belly (head) — e.g. Rectus femoris
🎯 Classification — Action of Muscles
| Role | Description |
|---|---|
| Prime mover | Responsible for initiating a particular movement (e.g. Brachialis = prime mover of elbow flexion) |
| Antagonist | Opposes the action of the prime mover (e.g. Triceps opposes Brachialis during elbow flexion) |
| Synergist | Helps the prime mover by fixing its origin or stabilizing the joint it acts on |
| Fixator (stabilizer) | Steadies & eliminates unwanted movement in proximal joints while distal joints are active |
⚡ Functions of the Skeletal Muscles
- Movement of the body
- Maintain body posture
- Produce energy
- Keep blood & lymph moving inside vessels
- Protect internal organs
- Stabilize the joints
MUSCULAR SYSTEM
🔬 3 Tissue Types
Skeletal: voluntary, somatic, striated, multinucleate
Smooth: involuntary, autonomic, spindle, uninucleate
Cardiac: involuntary, branched, no fatigue
🏗️ Construction
Belly → tendon/aponeurosis → bone
Origin (fixed) vs Insertion (mobile)
Epi-/Peri-/Endo-mysium coverings
🏷️ Naming Basis (6)
Shape, Number of origins, Size
Length, Location, Function
🧩 Fiber Arrangement
Parallel
Pennate (uni/bi/multi)
Oblique non-pennate (convergent/circular)
Multiple heads
🎯 Action Roles
Prime mover
Antagonist
Synergist
Fixator
1
Word Origin
"Muscle" ← Greek MUS (mouse). Belly = mouse body/head; Tendon = mouse tail.
2
Nerve Supply Rule
Skeletal = Somatic. Smooth & Cardiac = Autonomic.
3
Only Cardiac Branches
Cardiac muscle is the only type that is branched — fibers fuse together, single nucleus, never fatigues.
4
Origin vs Insertion
Origin = fixed (usually proximal). Insertion = mobile (usually distal) — moves toward origin on contraction.
5
-mysium Order
Epimysium (whole muscle) → Perimysium (fascicle/bundle) → Endomysium (single fiber) — outer to inner.
6
Biceps = 2 Heads
"BI-CEPS" = naming by number of origins, not shape. Compare Triceps (3 heads), Quadriceps (4 heads).
7
Pennate Muscles
"Pennate" = feather-like; fibers oblique to line of pull. Subtypes: unipennate, bipennate, multipennate.
8
Prime Mover vs Antagonist
Classic pair: Brachialis (prime mover, elbow flexion) ↔ Triceps (antagonist). They oppose each other's action.
9
Synergist vs Fixator
Synergist helps prime mover by stabilizing its origin. Fixator steadies proximal joints while distal joints move.
10
Tendon vs Aponeurosis
Both attach muscle to bone. Tendon = cord-like. Aponeurosis = broad & flat sheet.
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TERM
Word Origin
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"Muscle" ← Greek MUS (mouse). Belly = mouse body/head; Tendon = mouse tail.
TERM
Nerve Supply Rule
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Skeletal = Somatic.
Smooth & Cardiac = Autonomic.
Smooth & Cardiac = Autonomic.
TERM
Only Cardiac Branches
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Cardiac muscle is the only type that is branched — fibers fuse together, single nucleus, never fatigues.
TERM
Origin vs Insertion
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Origin = fixed (usually proximal).
Insertion = mobile (usually distal) — moves toward origin on contraction.
Insertion = mobile (usually distal) — moves toward origin on contraction.
TERM
-mysium Order
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Epimysium (whole muscle) → Perimysium (fascicle/bundle) → Endomysium (single fiber) — outer to inner.
TERM
Biceps = 2 Heads
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"BI-CEPS" = naming by number of origins, not shape. Compare Triceps (3 heads), Quadriceps (4 heads).
TERM
Pennate Muscles
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"Pennate" = feather-like; fibers oblique to line of pull. Subtypes: unipennate, bipennate, multipennate.
TERM
Prime Mover vs Antagonist
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Classic pair: Brachialis (prime mover, elbow flexion) ↔ Triceps (antagonist). They oppose each other's action.
TERM
Synergist vs Fixator
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Synergist helps prime mover by stabilizing its origin.
Fixator steadies proximal joints while distal joints move.
Fixator steadies proximal joints while distal joints move.
TERM
Tendon vs Aponeurosis
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Both attach muscle to bone. Tendon = cord-like.
Aponeurosis = broad & flat sheet.
Aponeurosis = broad & flat sheet.
Lecture 03
The Joints
Fibrous · Cartilaginous · Synovial Joints — Classification & Stability
🔗 Definitions
Joint (Articulation)
A point of contact between two or more bones
Arthrology
The science dealing with the study of joints
Two classification systems:
1) By nature of connecting substance → Fibrous (syn-desmosis) / Cartilaginous (syn-chondrosis) / Synovial (syn-ovial)
2) By range of movement → Synarthrosis (immovable) / Amphiarthrosis (slightly movable) / Diarthrosis (freely movable)
1) By nature of connecting substance → Fibrous (syn-desmosis) / Cartilaginous (syn-chondrosis) / Synovial (syn-ovial)
2) By range of movement → Synarthrosis (immovable) / Amphiarthrosis (slightly movable) / Diarthrosis (freely movable)
A. Fibrous Joints (Synarthroses)
- Bones connected by fibrous tissue; joint has no cavity; no or very limited movement
| Type | Description | Example |
|---|---|---|
| Sutures | Thin layer of fibrous tissue unites bones; no movement; some ossify in old age | Skull bones |
| Syndesmosis | Space between bones; fibrous tissue as a bundle (ligament) or sheet (interosseous membrane); slight movement | Inferior tibio-fibular joint |
| Gomphosis | Cone-shaped peg fits into a socket; no movement | Root of tooth in its bony socket |
B. Cartilaginous Joints (Amphiarthroses)
- Bones connected by cartilage (hyaline or fibrocartilage); no cavity; no/limited movement
| Type | Description | Example |
|---|---|---|
| Primary (Synchondrosis) | Connecting structure is hyaline cartilage; eventually ossifies | Epiphyseal plate (epiphysis↔diaphysis) |
| Secondary (Symphysis) | Bone ends covered by hyaline cartilage; connected by a flat disc of fibrocartilage; lies in median plane; allows limited movement | Pubic symphysis, intervertebral joints |
C. Synovial Joints (Diarthroses)
- Have a space between bones called the synovial cavity; wide range of movement
- Classified according to: shape of articulating surfaces & axes of movement
Structure of a Synovial Joint
- Bone ends covered by articular (hyaline) cartilage
- Surrounded by two layers: outer fibrous capsule + inner synovial membrane
- Capsule reinforced by ligaments; surrounded by muscles that produce movement
- Cartilage inside the joint → called a meniscus
- Synovial fluid: lubricates cartilage, allows free movement, nourishes cartilage/menisci/discs
🔄 Classification of Synovial Joints
| Axes | Type | Mechanism | Example |
|---|---|---|---|
| Uniaxial | Hinge | Convex surface of one fits concave surface of another | Elbow joint |
| Pivot | Pointed surface of one bone articulates with a ring formed by another bone + ligament | Superior radio-ulnar joint | |
| Biaxial | Saddle | Articular surface of one is saddle-shaped; the other fits into the "saddle" | Carpometacarpal joint of thumb |
| Ellipsoid (Condyloid) | Convex oval projection of one fits oval depression of another | Metacarpophalangeal joints / Wrist | |
| Multiaxial (Polyaxial) | Ball & Socket | Ball-like surface fits a cup-like depression | Shoulder & hip joints |
| Nonaxial | Plane | Articulating surfaces are flat or slightly curved | Intertarsal / intercarpal joints |
🛡️ Stability of Synovial Joints
- Shape of articular surfaces → determines what movements are possible
- Number & position of ligaments → unite bones & prevent excessive/undesirable motion
- Muscle tone & tendons crossing the joint
JOINTS
🦴 Fibrous (Synarthrosis)
Sutures — skull, no movement
Syndesmosis — ligament/membrane, slight movement
Gomphosis — tooth in socket
🦷 Cartilaginous (Amphiarthrosis)
Primary/Synchondrosis — hyaline, epiphyseal plate
Secondary/Symphysis — fibrocartilage, pubic symphysis
🦽 Synovial (Diarthrosis)
Synovial cavity + capsule + membrane
Meniscus, synovial fluid
Wide range of movement
🔄 By Axes/Shape
Uniaxial: Hinge, Pivot
Biaxial: Saddle, Ellipsoid
Multiaxial: Ball & Socket
Nonaxial: Plane
🛡️ Stability Factors
Shape of articular surfaces
Ligaments
Muscle tone & tendons
1
2 Classification Systems
By tissue type (Fibrous/Cartilaginous/Synovial) AND by movement range (Syn-/Amphi-/Di-arthrosis).
2
Gomphosis = Teeth Only
The only example of gomphosis is the tooth root fixed in its bony socket. No movement.
3
Synchondrosis Ossifies
Synchondrosis (hyaline cartilage, e.g. epiphyseal plate) eventually ossifies — temporary joint.
4
Symphysis = Midline
Secondary cartilaginous joints (symphysis) lie in the median plane — pubic symphysis, intervertebral discs.
5
Only Synovial Has a Cavity
Fibrous & cartilaginous joints have no cavity. Only synovial joints have a true joint (synovial) cavity.
6
Capsule = 2 Layers
Outer fibrous capsule + inner synovial membrane — reinforced by ligaments.
7
Meniscus
Cartilage found inside a synovial joint cavity is called a meniscus (e.g. knee joint).
8
Hinge vs Pivot
Both uniaxial. Hinge = convex-into-concave (elbow). Pivot = peg-in-ring (superior radioulnar).
9
Ball & Socket = Most Mobile
Multiaxial — ball-like surface in a cup-like depression. Shoulder & hip = most freely movable joints.
10
Plane Joint = Flat
Nonaxial; flat or slightly curved surfaces sliding past each other — intertarsal/intercarpal joints.
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TERM
2 Classification Systems
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By tissue type (Fibrous/Cartilaginous/Synovial) AND by
movement range (Syn-/Amphi-/Di-arthrosis).
movement range (Syn-/Amphi-/Di-arthrosis).
TERM
Gomphosis = Teeth Only
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The only example of gomphosis is the tooth root fixed in its bony socket. No movement.
TERM
Synchondrosis Ossifies
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Synchondrosis (hyaline cartilage, e.g. epiphyseal plate) eventually ossifies — temporary joint.
TERM
Symphysis = Midline
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Secondary cartilaginous joints (symphysis) lie in the median plane — pubic symphysis, intervertebral discs.
TERM
Only Synovial Has a Cavity
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Fibrous & cartilaginous joints have no cavity. Only synovial joints have a true joint (synovial) cavity.
TERM
Capsule = 2 Layers
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Outer fibrous capsule + inner
synovial membrane — reinforced by ligaments.
synovial membrane — reinforced by ligaments.
TERM
Meniscus
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Cartilage found inside a synovial joint cavity is called a meniscus (e.g. knee joint).
TERM
Hinge vs Pivot
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Both uniaxial. Hinge = convex-into-concave (elbow).
Pivot = peg-in-ring (superior radioulnar).
Pivot = peg-in-ring (superior radioulnar).
TERM
Ball & Socket = Most Mobile
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Multiaxial — ball-like surface in a cup-like depression. Shoulder & hip = most freely movable joints.
TERM
Plane Joint = Flat
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Nonaxial; flat or slightly curved surfaces sliding past each other — intertarsal/intercarpal joints.
Lecture 04
The Skin & Fascia
Skin Structure · Appendages · Lines of Cleavage · Functions · Superficial & Deep Fascia
🧴 Structure of the Skin
A. Epidermis
Top layer; stratified squamous epithelium. Contains keratinocytes (keratin = "waterproof"), melanocytes (melanin → skin color & UV absorption), Langerhans cells (defend against microorganisms), Merkel cells (touch sensation)
B. Dermis
Deeper layer; dense fibroconnective tissue (collagen + elastic fibers) → strength, support, flexibility. Contains blood vessels, lymph vessels, sensory receptors, hair follicles & glands
🧷 Skin Appendages
| Appendage | Parts / Details |
|---|---|
| Nail | Root (embedded, not exposed) + Body (exposed, free distal border) + Nail folds |
| Hair | Shaft (projects from surface) + Root + Follicle; Arrector pili muscle (sympathetic supply) makes hair stand vertical & compresses sebaceous glands |
| Sebaceous glands | Secrete sebum (oil); open into the hair follicle; absent in palms/soles; lubricate hair & soften skin |
| Sweat glands | 2 types — see table below |
| Eccrine Glands | Apocrine Glands | |
|---|---|---|
| Number | More numerous | Fewer |
| Distribution | All over the body | Armpits & genital area |
| Duct opening | Opens at skin surface | Opens into hair follicle |
| Secretion | Clear (water & salt) | Contains fatty acids & proteins |
✂️ Lines of Cleavage (Langer's Lines)
- Collagen & elastic fibers in the dermis are arranged in parallel bundles
- Langer's lines lie parallel to the collagen fibers of the dermis
- Surgical importance: a cut parallel to the lines remains closed & heals well (less scarring); a cut across the lines gapes and scars more
⚙️ Functions of the Skin
| Function | Details |
|---|---|
| A. Protection | Mechanical barrier, Chemical barrier, Biological barrier (against germs), Protection against UV radiation |
| B. Temperature regulation | Hot weather: sweating + widening of blood vessels (vasodilation) → heat radiation. Cold weather: narrowing of blood vessels (vasoconstriction) → heat storage |
| C. Absorption & Excretion | Absorbs fat-soluble vitamins (A,D,E,K) & some toxins; excretes water, salts, ammonia & urea via sweat |
| D. Synthesis of vitamin D | UV light activates a skin precursor → liver/kidney enzymes → calcitriol (active vitamin D) |
| E. 5th Sense | Sensory receptors transmit Pressure, Heat, Cold & Pain to the CNS |
🧵 The Fascial System
- Fascia = a fibrous tissue network lying between the skin and the underlying muscles & bones
- Composed of two layers: Superficial fascia (under the skin) & Deep fascia (deeply situated)
A. Superficial Fascia
- Lies beneath the skin & attached to it; contains fat cells, blood vessels, nerves, lymphatics, and muscles (e.g. platysma)
- Insulates the body & acts as an energy reserve
- Gives the body its contour (shape)
- Makes the skin slide over the deep fascia
- Gives passage to blood vessels, nerves & lymphatics travelling to the skin
B. Deep Fascia
- Tough, made of dense fibrous connective tissue
- Investing layer: layer beneath skin & superficial fascia, envelops the entire body (third envelope)
- Palmar & plantar aponeurosis: thickenings in the palm & sole
- Retinacula: localized thickenings around the wrist & ankle
- Intermuscular septum: tough membrane separating groups of muscles
- Capsule: layer surrounding individual organs (e.g. kidney)
- Loose areolar tissue: fascia filling among/around the organs
SKIN & FASCIA
🧴 Skin Structure
Epidermis: keratinocytes, melanocytes, Langerhans, Merkel
Dermis: collagen, elastic fibers, vessels, receptors
🧷 Appendages
Nail: root + body
Hair: shaft, follicle, arrector pili
Sebaceous (oil) glands
Sweat: Eccrine vs Apocrine
✂️ Langer's Lines
Parallel to collagen fibers
Cut parallel → heals well
Cut across → gapes/scars
⚙️ Functions (5)
Protection (4 barriers)
Temperature regulation
Absorption/Excretion
Vitamin D synthesis
5th sense
🧵 Fascia
Superficial: fat, vessels, platysma
Deep: investing layer, retinacula, aponeurosis, septum, capsule
1
Melanocytes
Produce melanin → gives skin its color AND absorbs damaging UV light.
2
Langerhans vs Merkel
Langerhans = immune defense. Merkel = touch sensation. Easy to confuse!
3
Arrector Pili = Sympathetic
Innervated by sympathetic nerves; contraction → hair stands up + compresses sebaceous gland (goosebumps).
4
Eccrine vs Apocrine
Eccrine: everywhere, opens to surface, watery. Apocrine: armpits/genitals, opens into follicle, fatty/protein secretion.
5
Surgical Incisions
Always cut parallel to Langer's lines for minimal scarring — classic exam point.
6
Temperature Control
Hot → sweat + vasodilation (heat loss). Cold → vasoconstriction (heat conservation).
7
Vitamin D Pathway
Skin (UV-activated precursor) → Liver → Kidney → Calcitriol (active vitamin D).
8
Platysma = Superficial Fascia
Unusual exception — the platysma muscle lies within the superficial fascia, not attached to bone like typical skeletal muscles.
9
Retinacula Location
Localized thickenings of deep fascia specifically around the wrist & ankle joints.
10
Capsule vs Areolar Tissue
Both are deep fascia types. Capsule = surrounds an individual organ (e.g. kidney). Loose areolar tissue = fills space among organs.
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TERM
Melanocytes
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Produce melanin → gives skin its color AND absorbs damaging UV light.
TERM
Langerhans vs Merkel
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Langerhans = immune defense.
Merkel = touch sensation. Easy to confuse!
Merkel = touch sensation. Easy to confuse!
TERM
Arrector Pili = Sympathetic
Tap to reveal 👆
Innervated by sympathetic nerves; contraction → hair stands up + compresses sebaceous gland (goosebumps).
TERM
Eccrine vs Apocrine
Tap to reveal 👆
Eccrine: everywhere, opens to surface, watery.
Apocrine: armpits/genitals, opens into follicle, fatty/protein secretion.
Apocrine: armpits/genitals, opens into follicle, fatty/protein secretion.
TERM
Surgical Incisions
Tap to reveal 👆
Always cut parallel to Langer's lines for minimal scarring — classic exam point.
TERM
Temperature Control
Tap to reveal 👆
Hot → sweat + vasodilation (heat loss).
Cold → vasoconstriction (heat conservation).
Cold → vasoconstriction (heat conservation).
TERM
Vitamin D Pathway
Tap to reveal 👆
Skin (UV-activated precursor) → Liver → Kidney → Calcitriol (active vitamin D).
TERM
Platysma = Superficial Fascia
Tap to reveal 👆
Unusual exception — the platysma muscle lies within the superficial fascia, not attached to bone like typical skeletal muscles.
TERM
Retinacula Location
Tap to reveal 👆
Localized thickenings of deep fascia specifically around the wrist & ankle joints.
TERM
Capsule vs Areolar Tissue
Tap to reveal 👆
Both are deep fascia types. Capsule = surrounds an individual organ (e.g. kidney).
Loose areolar tissue = fills space among organs.
Loose areolar tissue = fills space among organs.
Lecture 05
The Cardiovascular System
The Heart · Blood Vessels · Circulations · Anastomoses
❤️ Overview
Blood is pumped by the heart around a closed circuit of vessels, again and again, through the various "circulations" of the body.
It Consists Of
The Blood · The Heart · A closed system of vessels (Arteries, Veins, Capillaries)
The Blood
Complex mixture of cells, water, proteins & sugars — 55% plasma (liquid) / 45% cells (solid)
🫀 The Heart — General Description
- Four-chambered muscular organ, shaped & sized roughly like a closed fist
- Lies inside the thorax, between the 2 lungs, superior to the diaphragm, and to the left of the midline
The Pericardium
- Heart enclosed in a fibrous pericardium; inside lies the pericardial sac (serous membrane folded into 2 layers)
- Visceral layer (inner) + Parietal layer (outer); space between = pericardial space
Layers of the Heart Wall (3)
| Layer | Position |
|---|---|
| Epicardium | Outermost (= visceral pericardium) |
| Myocardium | Middle (muscular layer) |
| Endocardium | Inner |
📐 External Features of the Heart
- Roughly pyramidal / cone-shaped
- Apex: blunt rounded end, tip of the pyramid; formed of the left ventricle; directed anteriorly, inferiorly & to the left
Anterior surface
Sternocostal surface
Inferior surface
Diaphragmatic surface
Posterior surface
The base
🔲 Chambers & Valves of the Heart
- 2 Atria: thin-walled chambers that receive blood from the veins
- 2 Ventricles: thick-walled chambers that pump blood out through the arteries
| Valve Type | Location | Names |
|---|---|---|
| Atrioventricular ("cuspid") valves | Between atria & ventricles | Tricuspid (right), Bicuspid/Mitral (left) |
| Semilunar valves | At bases of vessels leaving the ventricles | Pulmonary & Aortic valves |
⚡ Conducting System of the Heart
An intrinsic regulating system that initiates & distributes the cardiac impulse over the heart.
1
SAN (Sinoatrial Node) — the pacemaker
2
AVN (Atrioventricular Node)
3
AV Bundle (Bundle of His)
4
Bundle branches (right & left)
5
Purkinje's fibers
🔄 Types of Circulation
| Type | Pathway |
|---|---|
| Coronary | Circulation of blood in the arteries supplying the heart itself |
| Pulmonary | Flow of blood between the heart & lungs (oxygenation) |
| Systemic | Flow of blood between the heart & the cells of the body |
| Portal | Flow of blood between the digestive tract & the liver |
🩸 Blood Vessels
| Arteries | Veins | Capillaries | |
|---|---|---|---|
| Direction | Away from the heart | Towards the heart | Connect arteries to veins |
| Branching | Get smaller → arterioles; branches → "anastomosis" | Have tributaries; capillaries→small venules→larger venules→veins | — |
| Special feature | Distribute blood via branches | Some contain valves to allow flow against gravity | Thin walls allow passage of materials to/from cells |
🔀 Anastomosis & Special Arteries
- Anastomosis: "end to end" communication between neighboring vessels
- Arterial anastomosis: artery to artery
- Arterio-venous anastomosis: arteriole to venule
- End arteries: arteries with no anastomoses — found in the retina & brain; sudden block → death of the tissue (infarction)
- Wavy arteries: have a wavy/tortuous course, able to stretch — examples: Facial, Lingual, Splenic & Uterine arteries
CARDIOVASCULAR SYSTEM
🫀 Heart Layers
Pericardium: fibrous + serous (visceral/parietal)
Wall: Epicardium → Myocardium → Endocardium
🔲 Chambers & Valves
2 Atria (receive) + 2 Ventricles (pump)
AV valves: Tricuspid/Mitral
Semilunar: Pulmonary/Aortic
⚡ Conducting System
SAN → AVN → Bundle of His
Bundle branches → Purkinje fibers
🔄 4 Circulations
Coronary — to heart
Pulmonary — to lungs
Systemic — to body cells
Portal — gut to liver
🩸 Vessels & Anastomosis
Arteries (away) vs Veins (towards)
End arteries: retina, brain
Wavy arteries: facial, lingual, splenic, uterine
1
Blood Composition
55% plasma (liquid) + 45% cells (solid) — a quick number to memorize.
2
Apex = Left Ventricle
The heart's apex is formed by the left ventricle, pointing anteriorly, inferiorly & to the left.
3
Epicardium = Visceral Pericardium
The outermost heart wall layer (epicardium) is the same as the visceral layer of the serous pericardium.
4
Atria Receive, Ventricles Pump
Simple rule: Atria = thin-walled, receive. Ventricles = thick-walled, pump.
5
SAN = Pacemaker
The Sinoatrial Node (SAN) is the heart's natural pacemaker — first in the conduction sequence.
6
Portal Circulation
Unique pathway: blood flows from the digestive tract to the liver (not directly to the heart first).
7
End Arteries = No Backup
Retina & brain arteries have no anastomoses — a sudden block causes tissue death (clinically critical).
8
4 Wavy Arteries
Facial, Lingual, Splenic, Uterine — all need to stretch with movement/distension.
9
Veins Have Valves
Some veins contain valves to push blood against gravity back to the heart — arteries do not have valves (except semilunar at their origin).
10
Capillary Function
Capillaries connect arteries to veins; their thin walls allow exchange of materials with the cells.
Answered: 0/30
Correct: 0
Wrong: 0
TERM
Blood Composition
Tap to reveal 👆
55% plasma (liquid) + 45% cells (solid) — a quick number to memorize.
TERM
Apex = Left Ventricle
Tap to reveal 👆
The heart's apex is formed by the left ventricle, pointing anteriorly, inferiorly & to the left.
TERM
Epicardium = Visceral Pericardium
Tap to reveal 👆
The outermost heart wall layer (epicardium) is the same as the visceral layer of the serous pericardium.
TERM
Atria Receive, Ventricles Pump
Tap to reveal 👆
Simple rule: Atria = thin-walled, receive.
Ventricles = thick-walled, pump.
Ventricles = thick-walled, pump.
TERM
SAN = Pacemaker
Tap to reveal 👆
The Sinoatrial Node (SAN) is the heart's natural pacemaker — first in the conduction sequence.
TERM
Portal Circulation
Tap to reveal 👆
Unique pathway: blood flows from the digestive tract to the liver (not directly to the heart first).
TERM
End Arteries = No Backup
Tap to reveal 👆
Retina & brain arteries have no anastomoses — a sudden block causes tissue death (clinically critical).
TERM
4 Wavy Arteries
Tap to reveal 👆
Facial, Lingual, Splenic, Uterine — all need to stretch with movement/distension.
TERM
Veins Have Valves
Tap to reveal 👆
Some veins contain valves to push blood against gravity back to the heart — arteries do not have valves (except semilunar at their origin).
TERM
Capillary Function
Tap to reveal 👆
Capillaries connect arteries to veins; their thin walls allow exchange of materials with the cells.
Lecture 06
The Lymphatic System
Lymph Formation & Transport · Lymphoid Tissue · Lymph Nodes · Thymus · Spleen
💧 Definition
- Part of both the cardiovascular and immune systems
- Reabsorbs & returns fluid escaped from blood vessels back to the venous system → heart
- This fluid is called "the lymph" — Lympha = clear water
⚗️ Lymph Formation
- Blood flows from arterioles → capillaries (rich in O₂ & nutrients)
- Fluid escapes from the capillaries with O₂ & nutrients
- Metabolism in cells → CO₂ & waste products, which diffuse back to the venous end of capillaries
- The remaining fluid in intercellular spaces is reabsorbed by lymph capillaries → becomes lymph
🧪 Lymph Capillaries
- Blind-ended tubes, slightly larger than blood capillaries
- Pick up the extracellular fluid
- Widely distributed except in: CNS, bone marrow, cornea & cartilage
- Lacteals: special lymphatic capillaries in the villi of the small intestine; absorb fatty lymph (chyle) containing fats & fat-soluble substances
🚚 Lymph Transport
Sequence: Lymph capillaries → Lymph vessels → Lymph trunks → Lymph ducts → Subclavian veins
| Duct | Drains |
|---|---|
| Right lymphatic duct | Right side of head/neck, thorax & right arm |
| Thoracic duct | The rest of the body (begins at cisterna chyli in the abdomen) |
🧬 Lymphatic Tissue — 2 Main Types
| MALT (Mucosa-Associated) | Lymphatic Organs | |
|---|---|---|
| Capsule | No capsule | Capsule present |
| Location | Connective tissue of almost all organs | Discrete organs |
| Role | Early detection of invaders | Filtration / immune maturation |
| Examples | Tonsils, Peyer's patches | Lymph nodes, Spleen, Thymus gland |
🟢 Lymph Nodes
- Collections of lymphoid tissue along the course of lymph vessels, arranged in groups
- Filter the lymph from harmful organisms & cell debris
- Afferent vessel: carries lymph towards the node
- Efferent vessel: carries clean lymph away from the node to the venous system (added to plasma)
🦋 Thymus
- Location: posterior to the sternum; divided into lobules
- The only lymphoid organ that does NOT fight antigens — functions as a "T-cell academy", distinguishing "self" from "foreign" tissue
- Produces hormone thymosin → stimulates lymphoid tissue maturation
- Involutes after puberty
🫘 Spleen
- Largest lymphoid organ
- Located on the left side of the abdominal cavity, under the diaphragm
- Supplied by the splenic artery & vein, entering/exiting at the hilum
Functions of the Spleen
- Site of lymphocyte proliferation
- Cleanses the blood from microorganisms
- Stores breakdown products of old (worn out) RBCs for later reuse
- Site of fetal erythrocyte production (till the 5th month of pregnancy)
- Stores blood platelets
⚙️ Functions of the Lymphatic System
- Return excess extracellular fluid to the CVS
- Filter lymph from bacteria or cell debris
- Lymphatic organs = sites for lymphocyte production, maturation & competency
- Lymph contains lymphocytes that patrol different body regions
- Transport digested lipids from intestinal lacteals
LYMPHATIC SYSTEM
💧 Formation
Arteriole → capillary → fluid escapes
Remaining fluid → lymph capillaries
Lacteals absorb chyle (fats)
🚚 Transport
Capillaries → Vessels → Trunks → Ducts
Right duct: head/neck/thorax/R arm
Thoracic duct: rest of body
🧬 Tissue Types
MALT: no capsule (tonsils, Peyer's)
Organs: capsule (nodes, spleen, thymus)
🦋 Thymus
T-cell academy, NOT antigen fighter
Thymosin hormone
Involutes after puberty
🫘 Spleen
Largest lymphoid organ
Filters blood, stores platelets
Fetal RBC production (<5 months)
1
Lympha = Clear Water
The word "lymph" comes from Latin lympha, meaning clear water.
2
No Lymphatics Here
Lymph capillaries are absent in: CNS, bone marrow, cornea, cartilage.
3
Lacteals = Fat Absorption
Found in intestinal villi; absorb chyle (fatty lymph) — unique to the small intestine.
4
Afferent In, Efferent Out
Easy memory trick: Afferent = Arriving. Efferent = Exiting (clean lymph to venous system).
5
Thymus ≠ Antigen Fighter
Unique exam point — the thymus is the only lymphoid organ that does NOT fight antigens directly.
6
Thymosin
Hormone produced by thymus → stimulates maturation of lymphoid tissue (T-cells).
7
Spleen = Largest Lymphoid Organ
Located left side, under diaphragm; supplied by splenic vessels at the hilum.
8
Spleen's Fetal Role
Produces fetal erythrocytes (RBCs) up to the 5th month of pregnancy.
9
MALT vs Lymphatic Organs
Key distinguishing feature = capsule. MALT has none (tonsils, Peyer's patches); organs have one (nodes, spleen, thymus).
10
Right Duct vs Thoracic Duct
Right duct = small area only (right head/neck/thorax/arm). Thoracic duct = everything else, starting at the cisterna chyli.
Answered: 0/30
Correct: 0
Wrong: 0
TERM
Lympha = Clear Water
Tap to reveal 👆
The word "lymph" comes from Latin lympha, meaning clear water.
TERM
No Lymphatics Here
Tap to reveal 👆
Lymph capillaries are absent in: CNS, bone marrow, cornea, cartilage.
TERM
Lacteals = Fat Absorption
Tap to reveal 👆
Found in intestinal villi; absorb chyle (fatty lymph) — unique to the small intestine.
TERM
Afferent In, Efferent Out
Tap to reveal 👆
Easy memory trick: Afferent =
Arriving. Efferent = Exiting (clean lymph to venous system).
Arriving. Efferent = Exiting (clean lymph to venous system).
TERM
Thymus ≠ Antigen Fighter
Tap to reveal 👆
Unique exam point — the thymus is the only lymphoid organ that does NOT fight antigens directly.
TERM
Thymosin
Tap to reveal 👆
Hormone produced by thymus → stimulates maturation of lymphoid tissue (T-cells).
TERM
Spleen = Largest Lymphoid Organ
Tap to reveal 👆
Located left side, under diaphragm; supplied by splenic vessels at the hilum.
TERM
Spleen's Fetal Role
Tap to reveal 👆
Produces fetal erythrocytes (RBCs) up to the 5th month of pregnancy.
TERM
MALT vs Lymphatic Organs
Tap to reveal 👆
Key distinguishing feature = capsule. MALT has none (tonsils, Peyer's patches); organs have one (nodes, spleen, thymus).
TERM
Right Duct vs Thoracic Duct
Tap to reveal 👆
Right duct = small area only (right head/neck/thorax/arm). Thoracic duct = everything else, starting at the cisterna chyli.
Lecture 07
The Respiratory System
Upper & Lower Respiratory Tract · Lungs · Pleura
🫁 Overview
- Lungs contain "alveoli" or "terminal air sacs"
- Gas exchange with blood occurs in the alveolar walls → respiratory zone
- The rest of the structures act only as a passageway to conduct air to the lungs → conducting zone — they also purify, humidify & warm the air
Upper Respiratory Tract
Nose, Pharynx (throat)
Lower Respiratory Tract
Larynx, Trachea, Bronchi, Lungs
👃 The Nose
- External nose: the only visible part of the respiratory system; air enters via 2 openings ("nostrils"); consists of cartilage & bones
- Nasal cavity: separated by the nasal septum into 2 cavities
Functions of the Nose
| Function | Mechanism |
|---|---|
| Passageway | For air |
| Cleans the air | Mucus membrane traps particles; tiny cilia move mucus backward to throat to be swallowed |
| Humidifies/warms air | 3 bony projections ("conchae") on lateral wall — rich in blood vessels (warm) + secrete mucus (humidify) |
| Smell | Mucus membrane at upper nasal cavity has olfactory receptors |
| Resonance | Nose & paranasal sinuses are resonating chambers for the voice |
Paranasal sinuses: hollow areas of skull bones opening into the nasal cavity; lined with mucus membrane (warming); make the skull lighter & the voice louder.
🗣️ Pharynx
- Common opening for the respiratory & digestive systems
- 3 regions: Nasopharynx, Oropharynx, Laryngopharynx
🔊 Larynx & Epiglottis
| Structure | Details |
|---|---|
| Larynx | Firm part felt in front of the neck; sits above the trachea; formed of cartilages; contains 2 vocal cords — vibration produces sound |
| Epiglottis | Part of the larynx; acts as a flap; keeps food from entering the air passage |
🌬️ Trachea & Bronchial Tree
- Starts at larynx, travels through upper thorax; ends at level T4/T5; about 10–12 cm long
- Divides into 2 primary bronchi (one to each lung); bifurcation point = "carina"
- Rests against the esophagus; kept open by C-shaped cartilage rings; posterior wall closed by muscle & connective tissue; lined by ciliated mucosa
Bronchial tree (like an upside-down tree): Bronchi → smaller → Bronchioles → smaller → Terminal bronchioles → give rise to Respiratory bronchioles
Alveoli: respiratory bronchioles terminate into alveolar ducts & sacs — the "respiratory exchange chambers" where O₂/CO₂ exchange occurs.
🫁 The Lungs
| Right Lung | Left Lung | |
|---|---|---|
| Lobes | 3 (Upper, Middle, Lower) | 2 (Upper, Lower) |
| Fissures | Oblique + Horizontal | Oblique only |
| Special feature | — | Cardiac notch |
Surfaces of Each Lung (lie within pleural cavities)
Apex
Up to the neck
Base
Rests on the diaphragm
Mediastinal surface
Contacts chest viscera; contains the hilum
Costal surface
Contacts the ribs
🌳 Lung Root (at the Hilum)
The root = bronchus + vessels entering each lung at the hilum:
- Primary Bronchus
- 2 Pulmonary Veins — carry oxygenated blood from each lung to the heart
- 1 Pulmonary Artery — carries deoxygenated blood to each lung
- Nerves
- Lymph vessels
🎈 Pleura
- A double membrane surrounding each lung
- Parietal layer: lines the chest wall, diaphragm & chest viscera
- Visceral layer: surrounds the lungs themselves
- Pleural cavity: the cavity in between the 2 layers
- Secretes fluid for lubrication (eases respiratory movement)
RESPIRATORY SYSTEM
👃 Upper Tract
Nose: cleans, warms, humidifies, smell, resonance
Pharynx: 3 regions, shared with GI
🔊 Larynx
2 vocal cords → sound
Epiglottis = flap, blocks food
🌬️ Trachea → Bronchial Tree
10-12cm, ends T4/5, carina
C-shaped cartilage rings
Bronchi → bronchioles → terminal → respiratory → alveoli
🫁 Lungs
Right: 3 lobes, 2 fissures
Left: 2 lobes, cardiac notch
Apex, Base, Mediastinal, Costal surfaces
🎈 Root & Pleura
Hilum: bronchus + 2 PV + 1 PA
Pleura: parietal + visceral + cavity
1
Respiratory vs Conducting Zone
Respiratory zone = alveoli (gas exchange). Conducting zone = everything else (passageway only).
2
Cilia Direction
Nasal cilia move mucus backward to the throat to be swallowed — not forward/outward.
3
Conchae Function
3 bony projections, rich in blood vessels (warm air) + mucus (humidify air).
4
Pharynx = Shared Tube
The pharynx is common to both respiratory & digestive systems — 3 regions: Naso-, Oro-, Laryngo-pharynx.
5
Carina = Bifurcation
The trachea divides into 2 primary bronchi at the carina — a key bronchoscopy landmark.
6
C-shaped Cartilage
Tracheal rings are C-shaped (incomplete posteriorly) — posterior wall closed by muscle, allowing the esophagus to bulge during swallowing.
7
Right = 3, Left = 2
Right lung has 3 lobes (extra space since heart is on the left); Left lung has 2 lobes + a cardiac notch to accommodate the heart.
8
Hilum Contents
At the hilum: 1 Bronchus + 2 Pulmonary Veins (oxygenated, to heart) + 1 Pulmonary Artery (deoxygenated, to lung) + nerves + lymphatics.
9
Pulmonary Vessels = Reversed
Unlike systemic vessels — pulmonary artery carries deoxygenated blood; pulmonary vein carries oxygenated blood.
10
Pleura = Double Membrane
Parietal (outer, lines chest wall) + Visceral (inner, on lung) + Pleural cavity (lubricating fluid) in between.
Answered: 0/30
Correct: 0
Wrong: 0
TERM
Respiratory vs Conducting Zone
Tap to reveal 👆
Respiratory zone = alveoli (gas exchange).
Conducting zone = everything else (passageway only).
Conducting zone = everything else (passageway only).
TERM
Cilia Direction
Tap to reveal 👆
Nasal cilia move mucus backward to the throat to be swallowed — not forward/outward.
TERM
Conchae Function
Tap to reveal 👆
3 bony projections, rich in blood vessels (warm air) + mucus (humidify air).
TERM
Pharynx = Shared Tube
Tap to reveal 👆
The pharynx is common to both respiratory & digestive systems — 3 regions: Naso-, Oro-, Laryngo-pharynx.
TERM
Carina = Bifurcation
Tap to reveal 👆
The trachea divides into 2 primary bronchi at the carina — a key bronchoscopy landmark.
TERM
C-shaped Cartilage
Tap to reveal 👆
Tracheal rings are C-shaped (incomplete posteriorly) — posterior wall closed by muscle, allowing the esophagus to bulge during swallowing.
TERM
Right = 3, Left = 2
Tap to reveal 👆
Right lung has 3 lobes (extra space since heart is on the left); Left lung has 2 lobes + a cardiac notch to accommodate the heart.
TERM
Hilum Contents
Tap to reveal 👆
At the hilum: 1 Bronchus + 2 Pulmonary Veins (oxygenated, to heart) +
1 Pulmonary Artery (deoxygenated, to lung) + nerves + lymphatics.
1 Pulmonary Artery (deoxygenated, to lung) + nerves + lymphatics.
TERM
Pulmonary Vessels = Reversed
Tap to reveal 👆
Unlike systemic vessels — pulmonary artery carries deoxygenated blood; pulmonary
vein carries oxygenated blood.
vein carries oxygenated blood.
TERM
Pleura = Double Membrane
Tap to reveal 👆
Parietal (outer, lines chest wall) + Visceral (inner, on lung) + Pleural cavity (lubricating fluid) in between.
Lecture 08
The Gastrointestinal System
Mouth · Pharynx · Esophagus · Stomach · Small & Large Intestine · Liver · Pancreas
🍽️ Overview
Digestive Tract
Mouth → Pharynx → Esophagus → Stomach → Small intestine → Large intestine
Digestive Organs (Accessory)
Teeth, Tongue, Salivary glands, Liver, Gall bladder, Pancreas
👄 The Mouth
- Oral cavity: bounded externally by lips & cheeks
- Vestibule: the space between lips/cheeks and the teeth
- Separated from the nasal cavity by the roof of the mouth, formed of: Hard palate (bone), Soft palate (muscle), Uvula (finger-like projection from soft palate)
The Teeth
| Adults (32 teeth) | Deciduous / Milk Teeth (20 teeth) | |
|---|---|---|
| Per half-jaw | 2 Incisors (biting), 1 Canine (tearing), 2 Premolars (grinding), 3 Molars (crushing) | 2 Incisors (central & lateral), 1 Canine, 2 Molars |
| Note | Last molar = "wisdom tooth" | Babies only — no premolars |
👅 Tongue & Salivary Glands
- Tongue: muscular organ covered with mucus membrane. Frenulum = fold attaching tongue's under-surface to floor of mouth. Papillae = rough dorsal projections, some carry taste receptors
| Gland | Location | Duct Opening |
|---|---|---|
| Parotid (largest) | Anterior & inferior to the ears | Vestibule, opposite upper 2nd molar |
| Sublingual | Beneath the tongue, under mucosa of mouth floor | Many ducts, open under the tongue |
| Submandibular | Floor of mouth, medial to mandible | Single duct, opens under the tongue |
Saliva contains bicarbonate and an enzyme that begins digestion of starch.
🔽 Pharynx & Esophagus
- Pharynx: 3 parts (Naso-, Oro-, Laryngo-pharynx). No digestion occurs here — function = swallowing + air passage
- Esophagus: muscular tube; passes from pharynx through thorax & diaphragm into the abdomen to join the stomach. Moves food via rhythmic peristalsis
🫃 The Stomach
- Thick-walled, J-shaped organ; left side of abdomen, deep to liver & diaphragm
- Continues with esophagus above, small intestine below
Functions of the Stomach
- Reservoir & mixes the food
- Starts digestion of protein & fats
- Activates some enzymes
- Destroys some bacteria
- Makes intrinsic factor that absorbs vitamin B12
- Absorbs alcohol & water
🌀 The Small Intestine
Extends from the pyloric sphincter to the ileocecal valve. 3 parts:
| Part | Key Features |
|---|---|
| Duodenum | C-shaped, ~25cm; receives bile (via common bile duct) & pancreatic secretions (via pancreatic duct) |
| Jejunum | Proximal 2/5 of small intestine; larger lumen, more folds; fewer arterial arcades, longer vasa recta |
| Ileum | Distal 3/5; smaller lumen, fewer folds; more arcades, shorter vasa recta; has Peyer's patches; most absorption occurs here; empties into cecum via the ileocecal valve |
🔄 The Large Intestine
- ~1.5 m long; begins lower right abdomen → ascends → crosses left to spleen → descends → terminates at anus
- Divided into: Cecum, Appendix, Ascending/Transverse/Descending/Sigmoid colon, Rectum, Anal canal
Differs from small intestine
No villi · Has taeniae coli · Haustration (sacculation) · Epiploic appendages
Main role
Receives undigested food, absorbs water & electrolytes, passes feces out
🫘 Liver, Gall Bladder & Pancreas
| Organ | Functions |
|---|---|
| Liver (largest gland, 4 lobes, upper right abdomen) | Makes bile · Detoxifies drugs/alcohol · Stores glycogen, vitamins (A,D,E,K), iron & cholesterol · Activates vitamin D · Fetal RBC production · Metabolizes absorbed nutrients |
| Gall bladder | Stores & concentrates bile; expels it into duodenum. Bile = yellowish-green fluid that emulsifies fats |
| Pancreas (mixed gland, posterior abdominal wall) | Endocrine: Islets of Langerhans → insulin & glucagon into blood. Exocrine: acini → pancreatic juice → duodenum |
GASTROINTESTINAL SYSTEM
👄 Mouth & Teeth
Oral cavity, vestibule, palate
32 teeth (2-1-2-3 per half jaw)
3 salivary gland pairs
🔽 Pharynx & Esophagus
Pharynx: no digestion, just passage
Esophagus: peristalsis
🫃 Stomach
J-shaped, left side
Intrinsic factor → B12
Starts protein/fat digestion
🌀 Small Intestine
Duodenum: bile + pancreatic juice
Jejunum: proximal 2/5
Ileum: distal 3/5, Peyer's patches
🔄 Large Intestine & Accessory Organs
No villi, taeniae coli, haustra
Liver: bile, detox, storage
Pancreas: endocrine + exocrine
1
Tooth Formula
Adults: 2 incisors, 1 canine, 2 premolars, 3 molars per half-jaw = 32 total. Babies: no premolars = 20 total.
2
Parotid = Largest
The parotid gland is the largest salivary gland; duct opens opposite the upper 2nd molar.
3
No Digestion in Pharynx
The pharynx's only role is swallowing & air passage — no digestion happens there.
4
Intrinsic Factor
Made by the stomach; essential for absorption of vitamin B12 in the ileum.
5
Jejunum vs Ileum
Jejunum = proximal 2/5, larger lumen, fewer arcades/longer vasa recta. Ileum = distal 3/5, Peyer's patches, most absorption.
6
Duodenum Receives 2 Ducts
Common bile duct (bile) + Pancreatic duct (pancreatic juice) both empty into the duodenum.
7
Large Intestine ≠ Villi
Large intestine has no villi (unlike small intestine) — instead has taeniae coli, haustra, epiploic appendages.
8
Bile = Fat Emulsifier
Made by liver, stored/concentrated in gallbladder, emulsifies fats in the duodenum.
9
Pancreas = Mixed Gland
Endocrine (islets → insulin/glucagon) + Exocrine (acini → pancreatic juice via pancreatic duct).
10
Liver = Largest Gland
4 lobes; makes bile, detoxifies, stores vitamins/glycogen/iron, activates vitamin D, metabolizes nutrients.
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TERM
Tooth Formula
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Adults: 2 incisors, 1 canine, 2 premolars, 3 molars per half-jaw = 32 total. Babies: no premolars =
20 total.
20 total.
TERM
Parotid = Largest
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The parotid gland is the largest salivary gland; duct opens opposite the upper 2nd molar.
TERM
No Digestion in Pharynx
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The pharynx's only role is swallowing & air passage — no digestion happens there.
TERM
Intrinsic Factor
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Made by the stomach; essential for absorption of vitamin B12 in the ileum.
TERM
Jejunum vs Ileum
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Jejunum = proximal 2/5, larger lumen, fewer arcades/longer vasa recta.
Ileum = distal 3/5, Peyer's patches, most absorption.
Ileum = distal 3/5, Peyer's patches, most absorption.
TERM
Duodenum Receives 2 Ducts
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Common bile duct (bile) + Pancreatic duct (pancreatic juice) both empty into the duodenum.
TERM
Large Intestine ≠ Villi
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Large intestine has no villi (unlike small intestine) — instead has taeniae coli, haustra, epiploic appendages.
TERM
Bile = Fat Emulsifier
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Made by liver, stored/concentrated in gallbladder, emulsifies fats in the duodenum.
TERM
Pancreas = Mixed Gland
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Endocrine (islets → insulin/glucagon) +
Exocrine (acini → pancreatic juice via pancreatic duct).
Exocrine (acini → pancreatic juice via pancreatic duct).
TERM
Liver = Largest Gland
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4 lobes; makes bile, detoxifies, stores vitamins/glycogen/iron, activates vitamin D, metabolizes nutrients.
Lecture 09
The Nervous System
CNS · PNS · Spinal Nerve · Autonomic Nervous System
🧠 Function of the Nervous System
The master system that controls & communicates all body systems together.
| Step | Description |
|---|---|
| 1. Sensory input | Sensory receptors detect stimuli from inside & outside the body |
| 2. Integration | Nervous system interprets & processes sensory input, decides what should be done |
| 3. Motor output | Effects a response by activating muscles or glands |
🔬 Structure — Cellular Level
1 · Neurons (Nerve Cells)
Structural & functional unit of the nervous system; specialized in transmitting nerve impulses; each has a cell body + processes (dendrites & axon)
2 · Neuroglia (Supporting Cells)
Accessory "nerve glue" cells — physiological support, protection & insulation in CNS & PNS. There are 10× as many neuroglia as neurons
🏛️ 1. Central Nervous System (CNS)
Consists of the Brain + Spinal Cord
| Component | Details |
|---|---|
| Brain | Lies within the skull; formed of cerebrum, cerebellum & brain stem (midbrain, pons, medulla) |
| Spinal Cord | Lies in upper 2/3 of vertebral canal; continuous above with medulla; outer white matter + inner gray matter; provides 2-way conduction; gives exit for 31 pairs of spinal nerves |
Meningeal Coverings (outer → inner)
- Dura mater (outer)
- Arachnoid mater (middle)
- Pia mater (inner)
Subarachnoid space (between arachnoid & pia) contains cerebrospinal fluid (CSF).
🌐 2. Peripheral Nervous System (PNS)
- Includes cranial & spinal nerves; divided into Somatic & Autonomic nervous systems
- Cranial nerves: 12 pairs — carry information to/from the brain
- Spinal nerves: 31 pairs — carry information to/from the spinal cord
Spinal Nerve — 2 Roots
| Root | Function |
|---|---|
| Ventral root | Motor (efferent) |
| Dorsal root (+ DRG) | Sensory (afferent) |
⚖️ Autonomic Nervous System
| Sympathetic | Parasympathetic | |
|---|---|---|
| Nickname | "Fight or Flight" | "Rest and Digest" |
| Division | Thoracolumbar | Craniosacral |
| Dominant when | Stress — anger, fear, anxiety, exercise | Relaxed (non-stress) states — normal organ function |
NERVOUS SYSTEM
⚙️ 3-Step Function
Sensory input
Integration
Motor output
🔬 Cell Types
Neurons: cell body + dendrites + axon
Neuroglia: 10× more numerous, support cells
🏛️ CNS
Brain: cerebrum, cerebellum, brain stem
Spinal cord: 31 pairs of nerves
Meninges: Dura, Arachnoid, Pia
🌐 PNS
12 cranial nerve pairs
31 spinal nerve pairs
Ventral root (motor) / Dorsal root (sensory)
⚖️ Autonomic NS
Sympathetic: thoracolumbar, fight/flight
Parasympathetic: craniosacral, rest/digest
1
3-Step Process
Sensory input → Integration → Motor output. The classic functional sequence of the nervous system.
2
Neuroglia >> Neurons
There are 10× as many neuroglia (support cells) as neurons in the nervous system.
3
CNS = Brain + Spinal Cord
Simple but essential: CNS consists of only the brain & spinal cord — everything else is PNS.
4
Meninges Order
Outer → Inner: Dura → Arachnoid → Pia (mnemonic: "DAP"). CSF is in the subarachnoid space.
5
31 Spinal Nerve Pairs
Spinal cord gives exit to 31 pairs of spinal nerves; cranial nerves = 12 pairs (don't mix these numbers up).
6
Ventral = Motor
Easy rule: Ventral = Voluntary/motor (efferent). Dorsal = sensory (afferent), with the DRG.
7
Sympathetic = Thoracolumbar
Sympathetic outflow originates from thoracic & lumbar spinal segments — fight or flight.
8
Parasympathetic = Craniosacral
Parasympathetic outflow originates from cranial nerves & sacral spinal segments — rest & digest.
9
White vs Gray Matter
In the spinal cord: outer = white matter (myelinated tracts), inner = gray matter (cell bodies) — opposite arrangement to the brain.
10
Brain Stem = 3 Parts
Brain = Cerebrum + Cerebellum + Brain stem (which itself = Midbrain + Pons + Medulla).
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Correct: 0
Wrong: 0
TERM
3-Step Process
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Sensory input → Integration → Motor output. The classic functional sequence of the nervous system.
TERM
Neuroglia >> Neurons
Tap to reveal 👆
There are 10× as many neuroglia (support cells) as neurons in the nervous system.
TERM
CNS = Brain + Spinal Cord
Tap to reveal 👆
Simple but essential: CNS consists of only the brain & spinal cord — everything else is PNS.
TERM
Meninges Order
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Outer → Inner: Dura →
Arachnoid →
Pia (mnemonic: "DAP"). CSF is in the subarachnoid space.
Arachnoid →
Pia (mnemonic: "DAP"). CSF is in the subarachnoid space.
TERM
31 Spinal Nerve Pairs
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Spinal cord gives exit to 31 pairs of spinal nerves; cranial nerves =
12 pairs (don't mix these numbers up).
12 pairs (don't mix these numbers up).
TERM
Ventral = Motor
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Easy rule: Ventral =
Voluntary/motor (efferent). Dorsal = sensory (afferent), with the DRG.
Voluntary/motor (efferent). Dorsal = sensory (afferent), with the DRG.
TERM
Sympathetic = Thoracolumbar
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Sympathetic outflow originates from thoracic & lumbar spinal segments — fight or flight.
TERM
Parasympathetic = Craniosacral
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Parasympathetic outflow originates from cranial nerves & sacral spinal segments — rest & digest.
TERM
White vs Gray Matter
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In the spinal cord: outer = white matter (myelinated tracts),
inner = gray matter (cell bodies) — opposite arrangement to the brain.
inner = gray matter (cell bodies) — opposite arrangement to the brain.
TERM
Brain Stem = 3 Parts
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Brain = Cerebrum + Cerebellum + Brain stem (which itself = Midbrain + Pons + Medulla).