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COMPLETE EXAM ANSWERS - HUMAN ANATOMY & PHYSIOLOGY

University Level | 10 Marks Each | Easy to Learn & Score

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UNIT 1

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Q1. Explain the Eukaryotic Cell Structure with Diagram and Functions

Definition

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DIAGRAM OF ANIMAL CELL (Eukaryotic)

         ┌─────────────────────────────────────┐
         │          CELL MEMBRANE              │
         │   ┌──────────────────────┐          │
         │   │   NUCLEUS            │ Nucleolus│
         │   │  (Nuclear membrane)  │  ●       │
         │   └──────────────────────┘          │
         │                                     │
         │  ┌──┐ Mitochondria    ┌───┐         │
         │  │  │ (Powerhouse)    │   │ Ribosome│
         │  └──┘                 └───┘         │
         │  ~~~~ Rough ER        ═══ Smooth ER │
         │  ┌────────────┐  Golgi Apparatus    │
         │  │  Vacuole   │  ┌┐┌┐┌┐            │
         │  └────────────┘  └┘└┘└┘            │
         │  ⊙ Centriole   ○ Lysosome          │
         │                                     │
         └─────────────────────────────────────┘

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ORGANELLES AND THEIR FUNCTIONS

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Key Points for Marks:

• Eukaryotic ribosomes are 80S (60S + 40S subunits)
• The outer nuclear membrane is continuous with ER
• Mitochondria have their own DNA (semi-autonomous)
• Lysosomes are the "suicidal bags" of the cell (term coined by De Duve)

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Q2. Detailed Note on Elementary Tissue (Epithelial Tissue)

Definition

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A. EPITHELIAL TISSUE

        EPITHELIAL TISSUE
              │
    ┌─────────┴──────────┐
    │                    │
Simple Epithelium    Stratified Epithelium
(single layer)       (multiple layers)
    │                    │
┌───┴───┐           ┌────┴────┐
Squamous  Cuboidal  Squamous  Cuboidal
Columnar  Pseudo-   Columnar  Transitional
          stratified

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B. CONNECTIVE TISSUE

1. Loose Connective Tissue - under skin, around organs (areolar tissue)
2. Dense Connective Tissue - tendons, ligaments
3. Cartilage - hyaline (joints), fibrocartilage (intervertebral discs), elastic (ear)
4. Bone - osseous tissue, support and protection
5. Blood - liquid connective tissue, transport
6. Adipose - fat storage, insulation

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C. MUSCLE TISSUE

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D. NERVOUS TISSUE

• Neurons: Functional units; dendrites receive, axon transmits impulses
• Neuroglial cells: Support cells (astrocytes, oligodendrocytes, microglia, Schwann cells)

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Q3. Significance of Mitosis and Meiosis

MITOSIS

MITOSIS FLOWCHART:
Interphase (DNA replication)
       ↓
PROPHASE → chromosomes condense, spindle forms
       ↓
METAPHASE → chromosomes align at equatorial plate
       ↓
ANAPHASE → sister chromatids separate to poles
       ↓
TELOPHASE → nuclear envelopes reform, cytokinesis
       ↓
Two identical daughter cells (2n → 2n)

1. Growth - increases cell number for body growth
2. Repair - replaces worn-out or injured cells
3. Asexual reproduction - in unicellular organisms
4. Maintains chromosome number - ensures genetic stability
5. Regeneration - healing of wounds

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MEIOSIS

MEIOSIS FLOWCHART:
Parent cell (2n)
       ↓
MEIOSIS I (Reductive division)
  ├── Prophase I: crossing over (genetic recombination)
  ├── Metaphase I: homologs align
  ├── Anaphase I: homologs separate
  └── Telophase I: 2 cells (n, each with 2 chromatids)
       ↓
MEIOSIS II (Equational division)
  ├── Similar to mitosis
  └── 4 haploid daughter cells (n)

1. Maintains species chromosome number - haploid gametes fuse to restore diploid number
2. Genetic variation - crossing over in Prophase I creates new gene combinations
3. Independent assortment - random distribution of chromosomes
4. Formation of gametes (sperm and ova)
5. Evolution - provides raw material for natural selection

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Comparison Table

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Q4. Skeletal System - Definition, Organization, and Appendicular Skeleton

Definition

Functions:

1. Support - structural framework
2. Protection - skull protects brain, ribs protect heart/lungs
3. Movement - levers for muscle action
4. Mineral storage - calcium and phosphate reservoir
5. Blood cell production - hematopoiesis in red bone marrow
6. Energy storage - fat in yellow bone marrow

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ORGANIZATION OF SKELETAL SYSTEM

SKELETAL SYSTEM (206 bones total)
         │
    ┌────┴────┐
AXIAL        APPENDICULAR
(80 bones)   (126 bones)
    │              │
┌───┴───┐    ┌─────┴──────┐
Skull   Verte- Pectoral  Pelvic
(29)   bral   Girdle    Girdle
       Col.   (4)       (2)
       (26)
Ribs(24)      Upper     Lower
Sternum(1)    Limbs(60) Limbs(60)

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APPENDICULAR SKELETON CLASSIFICATION (126 bones)

1. Pectoral (Shoulder) Girdle - 4 bones

• 2 Clavicles (collar bones)
• 2 Scapulae (shoulder blades)

2. Upper Limb - 60 bones (30 each side)

3. Pelvic Girdle - 2 bones

• 2 Hip bones (each formed by ilium, ischium, pubis)
• Together with sacrum forms pelvis

4. Lower Limb - 60 bones (30 each side)

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Q5. Structural and Functional Classification of Joints

Definition

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STRUCTURAL CLASSIFICATION (based on tissue between bones)

STRUCTURAL CLASSIFICATION
         │
    ┌────┼────┐
Fibrous  Cartilaginous  Synovial
(no cavity)  (no cavity)  (has cavity)
    │         │              │
Sutures  Synchondrosis  Most movable
Syndesmosis  Symphysis    joints
Gomphosis

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FUNCTIONAL CLASSIFICATION (based on degree of movement)

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Synovial Joint Types (Diarthroses)

Features of Synovial Joint:

         Bone
          │
     ┌────┴──────┐
     │ Articular │ ← Hyaline cartilage
     │ cartilage │
     │           │
     │  Synovial │ ← Filled with synovial fluid
     │   cavity  │   (lubricates, nourishes)
     │           │
     └────┬──────┘
    Joint capsule (fibrous outer + synovial inner)

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Q6. Constituents of Blood and Their Functions

Definition

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COMPOSITION OF BLOOD

BLOOD
  │
  ├── PLASMA (55%) - Liquid portion
  │     ├── Water (91%)
  │     ├── Plasma proteins (7%) - albumin, globulin, fibrinogen
  │     └── Electrolytes, nutrients, hormones, waste products
  │
  └── FORMED ELEMENTS (45%)
        ├── Erythrocytes (RBCs)   ~5 million/mm³
        ├── Leukocytes (WBCs)     ~7,000/mm³
        └── Thrombocytes (Platelets) ~2.5 lakh/mm³

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A. PLASMA COMPONENTS AND FUNCTIONS

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B. RED BLOOD CELLS (Erythrocytes)

• Shape: Biconcave disc (no nucleus in mature RBCs)
• Diameter: 7-8 µm
• Life span: 120 days; destroyed in spleen
• Contain: Hemoglobin (Hb) - carries O₂ and CO₂
• Function: O₂ transport, CO₂ transport, acid-base buffer

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C. WHITE BLOOD CELLS (Leukocytes)

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D. PLATELETS (Thrombocytes)

• Size: 2-4 µm, non-nucleated cell fragments
• Life span: 7-10 days
• Function: Primary hemostasis - form platelet plug; release clotting factors; vasoconstriction

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Q7. Coagulation Factors and Mechanism of Blood Coagulation

Coagulation Factors Table

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MECHANISM OF BLOOD COAGULATION

┌──────────────────────────────────────────────┐
│           COAGULATION CASCADE                │
│                                              │
│  EXTRINSIC PATHWAY    INTRINSIC PATHWAY      │
│  (seconds)            (minutes)              │
│  Triggered by:        Triggered by:          │
│  Tissue injury        Contact with           │
│  → Tissue Factor      collagen/glass         │
│  (Factor III)         → Factor XII (XII→XIIa)│
│       │                      │               │
│       ↓                      ↓               │
│  VII → VIIa            XI → XIa              │
│       │                      ↓               │
│       │               IX → IXa               │
│       │                      │               │
│       └──────────┬───────────┘               │
│                  ↓                           │
│            COMMON PATHWAY                    │
│            X → Xa (with Va, Ca²⁺)           │
│                  ↓                           │
│         Prothrombin (II) → Thrombin (IIa)    │
│                  ↓                           │
│         Fibrinogen (I) → Fibrin (soluble)    │
│                  ↓                           │
│         Factor XIIIa (+ Ca²⁺)               │
│                  ↓                           │
│         Cross-linked Fibrin (stable clot)    │
└──────────────────────────────────────────────┘

1. Vascular spasm - vasoconstriction reduces blood flow
2. Platelet plug formation - platelets adhere to exposed collagen via von Willebrand factor
3. Coagulation cascade - via extrinsic or intrinsic pathway → thrombin formation → fibrin clot

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Q8. Process of Erythropoiesis and Factors Required

Definition

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STAGES OF ERYTHROPOIESIS (Flowchart)

PLURIPOTENT STEM CELL
         ↓
MYELOID STEM CELL (CFU-GEMM)
         ↓
BFU-E (Burst Forming Unit - Erythroid)
         ↓
CFU-E (Colony Forming Unit - Erythroid)
         ↓
PROERYTHROBLAST
(large cell, basophilic, no Hb)
         ↓
BASOPHILIC ERYTHROBLAST
(active protein synthesis)
         ↓
POLYCHROMATOPHILIC ERYTHROBLAST
(Hb synthesis begins)
         ↓
ORTHOCHROMATIC ERYTHROBLAST (Normoblast)
(nucleus being extruded)
         ↓
RETICULOCYTE
(no nucleus; residual RNA remains)
(released into circulation)
         ↓
MATURE ERYTHROCYTE (RBC)
(7-8 µm, biconcave disc)

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FACTORS REQUIRED FOR ERYTHROPOIESIS

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Regulation:

Low O₂ (hypoxia)
       ↓
Kidney secretes EPO
       ↓
Bone marrow stimulated
       ↓
↑ RBC production
       ↓
Normal O₂ levels (negative feedback)

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Q9. Detailed Note on the Lymphatic System

Definition

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COMPONENTS

LYMPHATIC SYSTEM
       │
  ┌────┼──────────┬──────────┐
Vessels  Lymph    Lymphoid  Lymph
         (fluid)  Organs    Nodes
                    │
          ┌─────────┴────────┐
        Thymus  Spleen  Tonsils
        Bone marrow  MALT
                (Mucosa-Associated
                Lymphoid Tissue)

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LYMPH VESSELS

• Begin as blind-ended lymphatic capillaries in tissues
• Lymph capillaries → lymph vessels → lymph trunks → lymph ducts
• Right lymphatic duct - drains right upper body → right subclavian vein
• Thoracic duct - largest; drains rest of body → left subclavian vein

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LYMPHOID ORGANS

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FUNCTIONS OF LYMPHATIC SYSTEM

1. Fluid balance - returns excess interstitial fluid to blood (2-3 L/day)
2. Lipid absorption - lacteals in intestine absorb dietary fats as chylomicrons
3. Immune defense - lymphocytes (B and T cells) fight infections
4. Filtration - lymph nodes filter bacteria, cancer cells, debris
5. Transport - carries lymph from tissues back to venous circulation

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LYMPH FLOW

Tissue fluid (interstitial fluid)
         ↓
Lymph capillaries
         ↓
Lymph vessels (one-way valves)
         ↓
Lymph nodes (filtered here)
         ↓
Lymph trunks
         ↓
Thoracic duct / Right lymphatic duct
         ↓
Subclavian veins (returned to blood)

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Q10. Internal Anatomy of the Heart with Diagram

DIAGRAM OF HEART (Internal Anatomy)

                    AORTA
                      ↑
         ┌────────────┴────────────┐
         │    Pulmonary Artery     │
         │        ↑                │
         │  ┌─────┴────────────┐   │
Superior │  │   Left Atrium    │   │ Inferior
Vena    →│  │    (LA)    ←─────────── Pulmonary
Cava     │  │                  │   │ Veins
         │  │  Mitral Valve    │   │
         │  │  (Bicuspid) ↕    │   │
         │ Right Atrium ↕ Left Ventricle │
         │  (RA) → Tricuspid → (LV) Thickest │
         │         Valve        │   wall
         │          ↓           │
         │   Right Ventricle    │
         │      (RV)            │
         └──────────┬───────────┘
                    ↓
            Pulmonary Valve
                    ↓
            Pulmonary Artery
                    ↓
                   LUNGS

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CHAMBERS OF THE HEART

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VALVES OF THE HEART

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BLOOD CIRCULATION THROUGH HEART

Body → Superior/Inferior Vena Cava → Right Atrium
      → Tricuspid valve → Right Ventricle
      → Pulmonary valve → Pulmonary Artery → Lungs
      → Oxygenation → Pulmonary veins → Left Atrium
      → Mitral valve → Left Ventricle
      → Aortic valve → Aorta → Body

Wall Layers:

• Epicardium - outer visceral layer
• Myocardium - middle muscular layer (thickest, pumping)
• Endocardium - inner lining, lines chambers and valves

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UNIT 2

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Q12. Cardiac Cycle - Definition and Events

Definition

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PHASES OF THE CARDIAC CYCLE

CARDIAC CYCLE (0.8 sec total)
          │
    ┌─────┴──────┐
  SYSTOLE      DIASTOLE
  (0.3 sec)    (0.5 sec)
(Contraction) (Relaxation)

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7 PHASES (Based on Costanzo Physiology)

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PRESSURE-VOLUME LOOP (WIGGERS DIAGRAM - Key Points)

Left Ventricular Pressure (mmHg)
  120 ─────────────────────── (Max systolic)
        ╱ Ejection phase ╲
   80 ─╱                  ╲──── Aortic valve closes
      │  Isovolumetric      │
      │  Contraction        │ Isovolumetric
   0  │                     │ Relaxation
      └────────────────────────
       EDV(120ml)          ESV(50ml)
       End Diastolic Vol   End Systolic Vol
       Stroke Volume = EDV - ESV = 70 ml

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KEY VALUES TO REMEMBER

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HEART SOUNDS

• S1 (Lub): Closure of AV valves (mitral + tricuspid) at start of ventricular systole
• S2 (Dub): Closure of semilunar valves (aortic + pulmonary) at start of ventricular diastole
• S3: Abnormal; rapid ventricular filling; heard in heart failure
• S4: Abnormal; forceful atrial contraction; heard in ventricular hypertrophy

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Q13. Detailed Note on Arteries and Veins

Arteries

ARTERY (cross-section)
─────────────────────────────
│  Tunica Adventitia (outer) │ Connective tissue, nerves
│  ─────────────────────     │
│  Tunica Media (middle)     │ Smooth muscle + elastic fibers
│  ─────────────────────     │ (THICK in arteries)
│  Tunica Intima (inner)     │ Endothelium + basement membrane
│      LUMEN (small)         │
─────────────────────────────

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Veins

• Thinner walls than arteries (less smooth muscle)
• Large lumen
• Valves present (prevent backflow; absent in vena cava, portal vein, cerebral sinuses)
• Lower blood pressure

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COMPARISON: Arteries vs Veins

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IMPORTANT BLOOD VESSELS

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Q14. External Respiration and Regulation of Respiration

External Respiration

• Based on partial pressure gradients (Dalton's Law, Henry's Law)

ALVEOLUS
    │ O₂ diffuses in ↓       ↑ CO₂ diffuses out
    │
CAPILLARY (thin wall - 1 cell thick)
    │ Hemoglobin binds O₂
    │ CO₂ released
    ↓
OXYGENATED BLOOD to left heart

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REGULATION OF RESPIRATION

RESPIRATORY CONTROL CENTERS (in brainstem)
              │
   ┌──────────┼──────────┐
   │          │          │
DRG        VRG        Pneumotaxic
(Dorsal    (Ventral   Center
Resp Group) Resp Group) (Pons)
Inspiration Expiration  Limits
rhythm     (forced)    inspiration

A. NEURAL REGULATION

1. Medullary rhythmicity center:
   • DRG - generates basic rhythm of inspiration
   • VRG - active during forced breathing
2. Pontine centers:
   • Pneumotaxic center - inhibits inspiration, promotes expiration (fine-tuning)
   • Apneustic center - prolongs inspiration

B. CHEMICAL REGULATION (most important)

↑ CO₂ in blood
       ↓
↑ H⁺ ions (CO₂ + H₂O → H₂CO₃ → H⁺ + HCO₃⁻)
       ↓
Central chemoreceptors stimulated (medulla)
       ↓
↑ Rate and depth of breathing
       ↓
CO₂ blown off → pH normalizes

C. LUNG RECEPTORS

• Stretch receptors (Hering-Breuer reflex) - prevent over-inflation
• Irritant receptors - triggered by dust, smoke → cough, bronchoconstriction
• J-receptors (juxtacapillary) - in alveoli; respond to pulmonary congestion → rapid shallow breathing

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Q15. Gross Anatomy of the Respiratory System with Diagram

DIAGRAM

         NASAL CAVITY (filtration, warming, humidification)
              │
          PHARYNX
         (Nasopharynx → Oropharynx → Laryngopharynx)
              │
          LARYNX (voice box)
         (Epiglottis protects airway; vocal cords here)
              │
          TRACHEA (10-12 cm; 16-20 C-shaped cartilage rings)
              │
        ┌─────┴─────┐
    Left Bronchus   Right Bronchus (shorter, wider, more vertical)
        │               │
  Secondary         Secondary
  Bronchi            Bronchi
        │               │
  Tertiary Bronchi  (segmental)
        │
  Bronchioles (no cartilage)
        │
  Terminal Bronchioles
        │
  Respiratory Bronchioles
        │
  Alveolar Ducts
        │
  Alveolar Sacs → ALVEOLI (site of gas exchange)

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STRUCTURES IN DETAIL

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LUNGS

• Right lung: 3 lobes (upper, middle, lower); shorter, wider
• Left lung: 2 lobes (upper, lower); cardiac notch for heart
• Covered by pleura (visceral + parietal) with pleural cavity containing fluid (lubrication)
• Blood supply: Bronchial arteries (nutrition), pulmonary arteries (gas exchange)

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Q16. Mechanism of Respiration

Definition

BOYLE'S LAW (basis of respiration):

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MECHANISM

INSPIRATION (Active process)

Diaphragm contracts (moves down) + External intercostals contract
           ↓
Thoracic cavity volume INCREASES
           ↓
Lung volume INCREASES
           ↓
Intra-pulmonary pressure DECREASES (below atmospheric)
           ↓
Air flows INTO lungs (high → low pressure)

• Diaphragm descends 1.5 cm (normal breathing) to 7 cm (deep breathing)
• Atmospheric pressure: 760 mmHg; Intrapulmonary pressure drops to 758 mmHg

EXPIRATION (Passive in quiet breathing)

Diaphragm relaxes (moves up) + Elastic recoil of lungs
           ↓
Thoracic cavity volume DECREASES
           ↓
Lung volume DECREASES
           ↓
Intra-pulmonary pressure INCREASES (above atmospheric)
           ↓
Air flows OUT of lungs

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LUNG VOLUMES AND CAPACITIES

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UNIT 3 (GIT)

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Q17. Fat Digestion and Absorption in GIT

DIAGRAM OF GIT TRACT

ORAL CAVITY (mechanical digestion)
        │
    ESOPHAGUS (peristalsis)
        │
    STOMACH (churning; pepsin for proteins)
        │
  SMALL INTESTINE ← PANCREAS (lipase, bile)
  │  Duodenum     ← LIVER → GALLBLADDER (bile)
  │  Jejunum      (main digestion)
  │  Ileum        (absorption)
        │
  LARGE INTESTINE (water absorption)
  │  Cecum, Colon, Rectum
        │
     ANUS (defecation)

---

FAT DIGESTION

Dietary fats (Triglycerides)
        ↓
EMULSIFICATION by bile salts (from liver/gallbladder)
(breaks large fat globules into tiny droplets)
        ↓
Pancreatic LIPASE (most important)
+ Lingual lipase (minor, in mouth)
+ Gastric lipase (minor, in stomach)
        ↓
Triglycerides → 2 Fatty Acids + 1 Monoglyceride
        ↓
Form MICELLES with bile salts
(water-soluble transport vehicles)
        ↓
Micelles contact brush border of enterocytes
        ↓
Fatty acids and monoglycerides DIFFUSE into enterocytes

---

FAT ABSORPTION

Fatty acids + Monoglycerides enter enterocytes
        ↓
Reassembled into Triglycerides in smooth ER
        ↓
Combined with cholesterol, phospholipids, protein
        ↓
Form CHYLOMICRONS (lipoprotein particles)
        ↓
Exocytosed into LACTEALS (lymphatic capillaries in villi)
        ↓
Travel via lymphatic system → Thoracic duct
        ↓
Enter bloodstream at left subclavian vein
        ↓
Lipoprotein lipase in capillaries hydrolyzes triglycerides
        ↓
Fatty acids taken up by cells for energy/storage

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Q18. Anatomy of Stomach and Its Physiological Functions

ANATOMY

STOMACH (J-shaped organ)
         │
    ┌────┴────┐
PARTS:        REGIONS:
1. Cardia     ┌──────────────────┐
2. Fundus     │     FUNDUS       │  (stores gas)
3. Body/Corpus│                  │
4. Pylorus    │    BODY/CORPUS   │  (main digestive region)
              │                  │
              │    ANTRUM        │  (grinds food)
              └────────┬─────────┘
                  PYLORUS → PYLORIC SPHINCTER → Duodenum

• Mucosa (with rugae - folds allowing expansion)
• Submucosa
• Muscularis (3 layers: oblique, circular, longitudinal)
• Serosa

---

GASTRIC GLANDS AND SECRETIONS

---

PHYSIOLOGICAL FUNCTIONS

1. Storage - temporarily stores food (reservoir)
2. Mechanical digestion - churning movements mix food with gastric juice → chyme
3. Chemical digestion - pepsin digests proteins; lipase digests some fats
4. Sterilization - HCl (pH 1.5-2) kills most ingested bacteria
5. Intrinsic factor secretion - essential for Vitamin B12 absorption in ileum
6. Gastric motility - peristaltic waves move chyme toward pylorus
7. Regulation - gastrin, CCK regulate GI function
8. Absorption - minimal (alcohol, aspirin, some lipid-soluble drugs)

---

PHASES OF GASTRIC SECRETION

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Q19. Anatomy of Pancreas and Endocrine/Exocrine Secretions

ANATOMY

PANCREAS (mixed gland - 15 cm long)
         │
    ┌────┴────────────────┐
   HEAD    BODY         TAIL
(in C-loop  (crosses    (touches
of duodenum) spine)     spleen)
         │
   Main Pancreatic Duct (Duct of Wirsung)
   + Accessory Duct (Duct of Santorini)
         │
   Opens into AMPULLA OF VATER (with bile duct)
         │
     DUODENUM

---

EXOCRINE SECRETIONS (Acinar cells)

---

ENDOCRINE SECRETIONS (Islets of Langerhans)

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Q20. Anatomy, Histology and Functions of Small Intestine and Stomach

ANATOMY OF SMALL INTESTINE

---

HISTOLOGY OF SMALL INTESTINE

SURFACE AREA AMPLIFICATION (×600):
1. Plicae circulares (circular folds)   × 3
2. Villi (finger-like projections)      × 10
3. Microvilli (brush border)            × 20
                                         ─────
                                 Total: × 600

• Mucosa - simple columnar epithelium with enterocytes, goblet cells, enteroendocrine cells
• Submucosa - Brunner's glands (duodenum only - secrete alkaline mucus)
• Muscularis - inner circular + outer longitudinal smooth muscle
• Serosa - visceral peritoneum

• Central lacteal (lymphatic capillary for fat absorption)
• Blood capillaries (for glucose, amino acid absorption)
• Goblet cells (mucus secretion)
• Crypts of Lieberkühn (at base - cell renewal)

---

FUNCTIONS OF SMALL INTESTINE

1. Digestion - enzymes from brush border (maltase, lactase, sucrase, peptidases) complete digestion
2. Absorption - majority of nutrient absorption occurs here:
   • Glucose/amino acids → portal blood
   • Fats → lacteals → lymph
   • Fat-soluble vitamins (A,D,E,K) → lymph
   • Water-soluble vitamins → portal blood
   • B12 (ileum only) with intrinsic factor
   • Bile salts (ileum) → enterohepatic circulation
3. Secretion - succus entericus (intestinal juice, 1.5 L/day)
4. Motility - segmentation (mixing) and peristalsis (propulsion)
5. Immune defense - Peyer's patches, IgA secretion

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UNIT 6 - NERVOUS SYSTEM

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1. Structure and Function Areas of the Cerebrum

STRUCTURE OF CEREBRUM

• Largest part of brain (constitutes 83% of brain weight)
• Divided into two cerebral hemispheres by longitudinal fissure
• Connected by corpus callosum (largest white matter commissure)
• Surface covered by cerebral cortex (grey matter, 2-4 mm thick, ~10 billion neurons)
• Folds called gyri (ridges) separated by sulci (grooves)

---

LOBES OF CEREBRUM

            FRONTAL LOBE
           (Motor, Planning)
                 │
   Parietal ─────┼───── Occipital
  (Sensory)      │     (Vision)
                 │
           TEMPORAL LOBE
           (Hearing, Memory)
   Insula (deep - taste, visceral)

• Central sulcus (Fissure of Rolando) - separates frontal from parietal
• Lateral sulcus (Sylvian fissure) - separates temporal from frontal/parietal
• Parieto-occipital sulcus - separates parietal from occipital

---

FUNCTIONAL AREAS

---

HOMUNCULUS

• Motor homunculus (precentral gyrus) - body parts represented proportional to motor control needed (hands and face = large areas)
• Sensory homunculus (postcentral gyrus) - body parts proportional to sensory acuity

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2. Origin and Functions of the Autonomic Nervous System (ANS)

DEFINITION

ORIGIN

CNS
  │
  ├── SOMATIC NS (voluntary - skeletal muscle)
  │
  └── AUTONOMIC NS (involuntary - visceral)
            │
      ┌─────┴─────┐
  SYMPATHETIC   PARASYMPATHETIC
  (Thoracolumbar) (Craniosacral)
  T1-L2            CN III, VII, IX, X
                   S2-S4

---

GENERAL ORGANIZATION

• Preganglionic neuron (CNS → ganglion): myelinated, short (sympathetic) or long (parasympathetic)
• Postganglionic neuron (ganglion → effector): unmyelinated

• All preganglionic fibers: Acetylcholine (ACh) - cholinergic
• Parasympathetic postganglionic: ACh - cholinergic (muscarinic receptors)
• Sympathetic postganglionic: Norepinephrine (NE) - adrenergic (α and β receptors)
• Exception: sympathetic fibers to sweat glands and adrenal medulla release ACh

---

FUNCTIONS OF ANS

---

4. Functions of Different Cranial Nerves

---

5. Divisions of CNS and Functions of Hypothalamus and Cerebrum

DIVISIONS OF CNS

CENTRAL NERVOUS SYSTEM (CNS)
            │
     ┌──────┴───────┐
   BRAIN           SPINAL CORD
     │             (31 segments)
  ┌──┴──────────────────┐
FOREBRAIN  MIDBRAIN  HINDBRAIN
(Prosencephalon) (Mesencephalon) (Rhombencephalon)
     │                    │
┌────┴──┐          ┌──────┴──────┐
Cerebrum Diencephalon Pons  Medulla Cerebellum
         (Thalamus,
          Hypothalamus)

FUNCTIONS OF HYPOTHALAMUS

FUNCTIONS OF CEREBRUM (summary)

• Voluntary motor control
• Sensory processing and interpretation
• Higher cognitive functions (thinking, reasoning, planning)
• Language (Broca's and Wernicke's areas)
• Emotions and personality
• Learning and memory
• Consciousness and awareness (Detailed in Q1 of this unit above)

---

UNIT 7 - KIDNEY & ENDOCRINE

---

1. Nephron Diagram and Urine Formation

DIAGRAM OF NEPHRON

NEPHRON (functional unit of kidney):

Glomerulus (capillary tuft)
    │
Bowman's Capsule
    │
Proximal Convoluted Tubule (PCT)
    │
Loop of Henle
  ├── Descending limb (thin, permeable to water)
  └── Ascending limb (thick, impermeable to water; active NaCl transport)
    │
Distal Convoluted Tubule (DCT)
    │
Collecting Duct (CD)
    │
Renal Pelvis → Ureter → Bladder → Urethra

---

HOW URINE IS FORMED (3 Processes)

1. GLOMERULAR FILTRATION

Blood enters Glomerulus (high pressure ~60 mmHg)
           ↓
Filtration across glomerular membrane
(3 layers: endothelium, basement membrane, podocytes)
           ↓
Glomerular Filtrate = plasma minus proteins & cells
GFR = 125 mL/min = 180 L/day

---

2. TUBULAR REABSORPTION

180 L filtrate/day
           ↓ 99% reabsorbed
Only 1.5 L becomes urine

PCT:   Glucose, AA, Na⁺, Cl⁻, HCO₃⁻, 65% water (obligatory)
Loop:  Descending: water; Ascending: NaCl (no water)
DCT:   Na⁺ (aldosterone-dependent), Ca²⁺ (PTH-dependent)
CD:    Water (ADH-dependent), urea

---

3. TUBULAR SECRETION

H⁺, K⁺, NH₄⁺, drugs, toxins, creatinine
Secreted FROM peritubular capillaries INTO tubule lumen
Purpose: pH regulation, K⁺ balance, removal of waste

---

FLOWCHART OF URINE FORMATION

Blood → Glomerular filtration (180 L/day filtrate)
                  ↓
         Tubular reabsorption (178.5 L reabsorbed)
                  ↓
         Tubular secretion (waste added)
                  ↓
         URINE ~1.5 L/day

---

2. Structure of Kidney and Its Functions

STRUCTURE

KIDNEY (cross-section):

         Cortex (outer)
         │  Contains glomeruli, PCT, DCT
         │
         Medulla (inner)
         │  Pyramids (8-18 per kidney)
         │  Papillae (tips of pyramids)
         │  Contains loops of Henle, collecting ducts
         │
    Renal pelvis → Ureter
         │
    Hilum (medial):
    Renal artery enters, Renal vein exits, Ureter exits

• Cortical nephrons (85%) - short loops
• Juxtamedullary nephrons (15%) - long loops; important for concentration

---

BLOOD SUPPLY

Abdominal Aorta
    ↓
Renal Artery
    ↓
Segmental arteries → Interlobar → Arcuate → Interlobular → Afferent arteriole
    ↓                                                              ↓
                                                          Glomerulus
                                                              ↓
                                                     Efferent arteriole
                                                              ↓
                                                   Peritubular capillaries/Vasa recta
                                                              ↓
                                            Interlobular vein → Arcuate → Renal Vein

---

FUNCTIONS OF THE KIDNEY

1. Urine formation (filtration, reabsorption, secretion)
2. Fluid balance - regulates blood volume
3. Electrolyte balance - Na⁺, K⁺, Ca²⁺, Cl⁻, HCO₃⁻
4. Acid-base balance - excretes H⁺, reabsorbs HCO₃⁻
5. Blood pressure regulation - via RAAS (Renin-Angiotensin-Aldosterone System)
6. Erythropoiesis - secretes erythropoietin (EPO) → stimulates RBC production
7. Calcium metabolism - activates Vitamin D (1,25-dihydroxycholecalciferol)
8. Excretion - removes metabolic waste (urea, creatinine, uric acid, drugs)
9. Gluconeogenesis - in starvation

---

3. Hormones of the Pituitary Gland

PITUITARY GLAND (Hypophysis)

• Size: pea-sized gland; located in sella turcica of sphenoid bone
• Connected to hypothalamus by pituitary stalk
• Two lobes: Anterior (Adenohypophysis) and Posterior (Neurohypophysis)

---

ANTERIOR PITUITARY HORMONES

---

POSTERIOR PITUITARY HORMONES (Stored, not synthesized here)

---

4. Thyroid Hormone - Synthesis, Storage, Release, Functions

THYROID GLAND ANATOMY

• Located in anterior neck; bilobed with isthmus
• Functional unit: follicle (lined by follicular cells; filled with colloid containing thyroglobulin)
• Parafollicular C cells secrete calcitonin

---

SYNTHESIS OF THYROID HORMONES

SYNTHESIS (in follicular cells):
Step 1: Iodide trapping
         Blood I⁻ → Follicular cell (via Na⁺/I⁻ symporter) [stimulated by TSH]

Step 2: Oxidation of iodide
         I⁻ → I₂ (by thyroid peroxidase, TPO) [blocked by PTU, methimazole]

Step 3: Organification (iodination of tyrosine)
         Thyroglobulin (Tg) + I₂ → MIT (monoiodotyrosine) + DIT (diiodotyrosine)

Step 4: Coupling
         MIT + DIT → T3 (triiodothyronine)
         DIT + DIT → T4 (thyroxine)
         (by TPO - also blocked by PTU)

Step 5: Storage
         T3, T4 stored in colloid as thyroglobulin complex

---

RELEASE OF THYROID HORMONES

TSH (from pituitary) stimulates:
         ↓
Endocytosis of colloid into follicular cells
         ↓
Proteolysis of thyroglobulin → T3 + T4 released
         ↓
T3 + T4 enter blood (bound to TBG = thyroxine-binding globulin)
         ↓
T4 is major secretory product (80%)
T3 is more potent (4x more active)
T4 → T3 conversion occurs in peripheral tissues (by 5'-deiodinase)

---

FUNCTIONS OF THYROID HORMONES

1. Metabolic rate - ↑ BMR; ↑ O₂ consumption; ↑ heat production (calorigenic effect)
2. Growth and development - essential for brain development in fetus/newborn; deficiency → cretinism
3. Cardiovascular - ↑ heart rate, cardiac output, blood pressure
4. Nervous system - maintains normal CNS function; deficiency → slow reflexes, depression
5. Protein synthesis - ↑ at physiological doses; catabolic at high doses
6. Carbohydrate metabolism - ↑ glucose absorption, glycogenolysis, gluconeogenesis
7. Fat metabolism - ↑ lipolysis; ↓ cholesterol (clinical: hypothyroid → hypercholesterolemia)
8. Muscle function - maintains normal muscle tone and strength
9. Reproductive function - needed for normal sexual function; deficiency → anovulation, infertility

Hypothalamus → TRH
      ↓
Pituitary → TSH
      ↓
Thyroid → T3, T4 (negative feedback on hypothalamus + pituitary)

---

5. Physiological Role of Adrenal Cortical Hormones

ADRENAL GLAND ANATOMY

• Sits on top of each kidney
• Outer cortex (80%) + Inner medulla (20%)

ADRENAL CORTEX (3 zones):
  Zona Glomerulosa  → MINERALOCORTICOIDS (Aldosterone)
  Zona Fasciculata  → GLUCOCORTICOIDS (Cortisol) ← main zone
  Zona Reticularis  → ANDROGENS (DHEA, Androstenedione)
Mnemonic: "GFR" (like glomerular filtration rate!)

---

MINERALOCORTICOIDS (Aldosterone)

• Acts on DCT and collecting duct of kidney
• ↑ Na⁺ reabsorption (retains salt and water → ↑ blood volume/pressure)
• ↑ K⁺ excretion
• ↑ H⁺ excretion

---

GLUCOCORTICOIDS (Cortisol)

• Excess → Cushing's syndrome (obesity, striae, hypertension, diabetes)
• Deficiency → Addison's disease (weakness, hypotension, hyperpigmentation)

---

ANDROGENS (DHEA, Androstenedione)

• Converted to estrogen in peripheral tissues (adipose) - important in post-menopausal women
• Contribute to pubic/axillary hair growth (adrenarche)
• Deficiency → loss of pubic/axillary hair in women

---

UNIT 8 - REPRODUCTION

---

1. Phases of the Female Reproductive Cycle (Menstrual Cycle)

Definition

---

PHASES AND HORMONAL CONTROL

MENSTRUAL CYCLE (28 days)
         │
  ┌──────┼──────────────────────┐
  │      │                      │
Days 1-5 Days 6-13   Day 14  Days 15-28
MENSTRUAL PROLIFERATIVE OVULATION SECRETORY
Phase    (Follicular)          (Luteal)

---

PHASE-BY-PHASE DETAIL

---

HORMONAL INTERPLAY FLOWCHART

Hypothalamus → GnRH (pulsatile)
      ↓
Anterior Pituitary → FSH + LH
      ↓
Ovarian Follicles → Estrogen ↑
      ↓
Positive feedback → LH surge (Day 13-14)
      ↓
OVULATION (Day 14)
      ↓
Corpus Luteum → Progesterone + Estrogen
      ↓
If no pregnancy:
Corpus luteum degenerates → Progesterone ↓
      ↓
Menstruation (Day 1 of next cycle)

---

2. Spermatogenesis and Oogenesis

SPERMATOGENESIS

SPERMATOGENESIS:
Spermatogonium (2n) ← Type A (stem cell)
         ↓ Mitosis
Primary Spermatocyte (2n)
         ↓ MEIOSIS I
2 Secondary Spermatocytes (n)
         ↓ MEIOSIS II
4 Spermatids (n)
         ↓ SPERMIOGENESIS (maturation)
4 Spermatozoa (n)
         ↓ Released into lumen
         ↓ Move to epididymis for maturation (2-12 days)
Mature Spermatozoa

• FSH → stimulates Sertoli cells → supports spermatogenesis
• LH → stimulates Leydig cells → testosterone production
• Testosterone → essential for spermatogenesis

• Head (nucleus + acrosome with enzymes for egg penetration)
• Midpiece (mitochondria for energy)
• Tail (flagellum for motility)

---

OOGENESIS

OOGENESIS:
Primary Oocyte (2n) ← formed in fetal life
(arrested in PROPHASE I until puberty)
         ↓ At puberty - MEIOSIS I resumes
Secondary Oocyte (n) + First Polar Body
(arrested in METAPHASE II)
         ↓ Released at OVULATION
(MEIOSIS II completed only if fertilized)
         ↓ After fertilization
Mature Ovum (n) + Second Polar Body
         ↓
Fertilization → Zygote (2n)

---

COMPARISON

---

3. Contraceptives - Detailed Note

Definition

---

CLASSIFICATION

CONTRACEPTIVE METHODS
          │
  ┌───────┼──────────────────────────┐
Natural  Barrier  Hormonal  Intrauterine  Surgical
Methods  Methods  Methods   Devices       Methods

---

NATURAL METHODS

---

BARRIER METHODS

---

HORMONAL METHODS

---

INTRAUTERINE DEVICES (IUD)

---

SURGICAL METHODS

---

4. Hormones and Feedback Mechanisms

Definition

Classification of Hormones

---

FEEDBACK MECHANISMS

NEGATIVE FEEDBACK (Most common - maintains homeostasis)

Hypothalamus → Releasing hormone
        ↓
Anterior Pituitary → Tropic hormone
        ↓
Target gland → Hormone
        ↓
NEGATIVE FEEDBACK (hormone inhibits hypothalamus + pituitary)
        ↓
Hormone levels return to normal

Example: TRH → TSH → T3/T4 → inhibits TRH and TSH
Example: CRH → ACTH → Cortisol → inhibits CRH and ACTH

POSITIVE FEEDBACK (Amplifies response - less common)

Low estrogen → FSH secretion → follicle growth → MORE estrogen
        ↓
When estrogen is HIGH → POSITIVE FEEDBACK → LH surge → Ovulation
(then switches back to negative feedback)

Other example: Oxytocin during labor:
Cervical stretch → Oxytocin → Uterine contraction → MORE cervical stretch → MORE oxytocin
(cycle ends at delivery)

---

UNIT 9 - SPECIAL SENSES

---

1. Diagram of Eye and Physiology of Vision

DIAGRAM OF EYE

                Pupil (opening)
                  ●
         ─────────────────────
        │  Cornea (transparent)│
  ──────┤──────────────────────├──────
  Sclera│  Anterior Chamber    │ Sclera
  (white│  (aqueous humor)     │(white)
  coat) │  Lens (biconvex)     │
        │  Iris (controls pupil│
        │  size)               │
        │  Posterior Chamber   │
        │  (vitreous humor)    │
        │  Retina (innermost)  │
  ──────┤──────────────────────├──────
        │  Choroid (vascular)  │
        │  Fovea centralis     │ (sharpest vision)
        │  Optic disc          │ (blind spot)
         ─────────────────────
              Optic Nerve → Brain

---

LAYERS OF EYE WALL

1. Outer (fibrous): Sclera (white, protective) + Cornea (transparent, refracts light)
2. Middle (vascular): Choroid (blood supply) + Ciliary body (aqueous humor + lens shape) + Iris (pupil size)
3. Inner (neural): Retina (photoreceptors)

---

RETINAL CELLS

---

PHYSIOLOGY OF VISION - PHOTOTRANSDUCTION

LIGHT → hits Retina
              ↓
Rhodopsin (rod pigment) = Opsin + Retinal (11-cis form)
              ↓ light energy
Retinal changes shape: 11-cis → all-trans retinal (bleaching)
              ↓
Rhodopsin activated → Transducin (G-protein) activated
              ↓
Phosphodiesterase activated → cGMP hydrolyzed
              ↓
Na⁺ channels CLOSE (normally open in dark)
              ↓
Membrane HYPERPOLARIZES (becomes more negative)
              ↓
Less glutamate released by rods
              ↓
Bipolar cells → Ganglion cells → Optic nerve → Brain (occipital lobe)

---

VISUAL PATHWAY

Light → Retina → Optic Nerve (CN II)
      ↓
Optic Chiasm (nasal fibers cross)
      ↓
Optic Tract
      ↓
Lateral Geniculate Nucleus (LGN) of thalamus
      ↓
Optic Radiation
      ↓
Primary Visual Cortex (V1) - Occipital lobe (calcarine sulcus)
      ↓
Visual Association Areas → perception, recognition

---

2. Diagram of Ear and Physiology of Hearing

DIAGRAM OF EAR

EXTERNAL EAR    MIDDLE EAR      INNER EAR
                                 ┌─────────────┐
Pinna →       Malleus ─┐        │  Cochlea     │
Auditory      Incus    ├──────→ │  (hearing)   │
Canal →       Stapes ─┘         │             │
Tympanic                        │  Semicircular│
Membrane →                      │  Canals      │
                                 │  (balance)   │
             Eustachian tube     └─────────────┘
             (to nasopharynx)         ↓
                                 Cochlear nerve (CN VIII)
                                       ↓
                                 Auditory cortex
                                 (temporal lobe)

---

PHYSIOLOGY OF HEARING

Sound waves → Pinna (collects and focuses)
      ↓
External auditory canal
      ↓
Tympanic membrane VIBRATES
      ↓
Ossicles (Malleus → Incus → Stapes)
(amplify sound 22x through lever action + area ratio)
      ↓
Oval window (stapes footplate)
      ↓
Perilymph in scala vestibuli vibrates
      ↓
Basilar membrane in Organ of Corti vibrates
(HIGH frequency → base; LOW frequency → apex)
      ↓
Stereocilia of hair cells BENT
      ↓
Mechanically-gated ion channels OPEN
      ↓
K⁺ enters → Depolarization of hair cells
      ↓
Neurotransmitter (glutamate) released
      ↓
Cochlear nerve → CN VIII → Brainstem → Thalamus (medial geniculate)
      ↓
Primary Auditory Cortex (Heschl's gyrus, Temporal lobe)
      ↓
Perception of SOUND

---

3. Anatomy of Skin with Diagram and Functions

DIAGRAM OF SKIN

SURFACE (outer)
────────────────────────────────────
EPIDERMIS (stratified squamous)
 Layer 1: Stratum Corneum (dead, keratinized cells)
 Layer 2: Stratum Lucidum (only in thick skin - palms/soles)
 Layer 3: Stratum Granulosum (keratohyalin granules)
 Layer 4: Stratum Spinosum (prickle cells)
 Layer 5: Stratum Basale (stem cells; melanocytes)
────────────────────────────────────
DERMIS (connective tissue)
 Papillary dermis (collagen, capillaries, Meissner corpuscles)
 Reticular dermis (dense collagen, sweat glands, hair follicles,
                   Pacinian corpuscles, sebaceous glands)
────────────────────────────────────
HYPODERMIS (subcutaneous fat layer)
 Adipose tissue, large blood vessels, nerves

---

CELLS OF EPIDERMIS

---

FUNCTIONS OF SKIN

1. Protection - barrier against microbes, UV, chemicals, mechanical damage
2. Thermoregulation - sweat glands (cooling); vasodilation/vasoconstriction; subcutaneous fat (insulation)
3. Sensation - touch (Meissner), pressure (Pacinian), pain (free nerve endings), temperature
4. Vitamin D synthesis - UV → 7-dehydrocholesterol → Vitamin D3 (cholecalciferol)
5. Excretion - sweat removes small amounts of urea, salts
6. Water balance - prevents excessive water loss (but ~300-400 mL/day insensible loss)
7. Immunity - Langerhans cells process antigens; IgA in sweat
8. Absorption - limited; some drugs applied topically (nitroglycerine patch, estrogen patch)

---

4. Tongue - Detailed Account and Diseases

ANATOMY OF TONGUE

• Muscular organ attached to floor of mouth by frenulum
• Root (posterior 1/3) and Body (anterior 2/3) separated by sulcus terminalis (V-shaped groove)
• Dorsum (upper surface) covered by papillae

---

PAPILLAE AND TASTE

---

FIVE BASIC TASTES

---

NERVE SUPPLY

• Anterior 2/3 taste: Facial nerve (CN VII) via chorda tympani
• Posterior 1/3 taste: Glossopharyngeal nerve (CN IX)
• Posterior epiglottis: Vagus (CN X)
• General sensation (touch, pain): Lingual nerve (branch of CN V3)

---

DISEASES OF THE TONGUE

---

UNIT 10 - SPORTS & EXERCISE PHYSIOLOGY

---

1. Physiological Changes Due to Ageing and Benefits of Regular Exercise

PHYSIOLOGICAL CHANGES DUE TO AGEING

---

BENEFITS OF REGULAR EXERCISE

EXERCISE
    │
    ├── CARDIOVASCULAR: ↓ resting HR, ↓ BP, ↑ stroke volume,
    │                   ↑ HDL cholesterol, ↓ atherosclerosis risk
    │
    ├── RESPIRATORY: ↑ lung capacity, ↑ efficiency of gas exchange
    │
    ├── MUSCULOSKELETAL: ↑ muscle mass/strength, ↑ bone density,
    │                    ↑ joint flexibility
    │
    ├── METABOLIC: ↑ insulin sensitivity, ↓ blood glucose,
    │              ↑ BMR, ↓ obesity
    │
    ├── PSYCHOLOGICAL: ↑ serotonin/endorphins → ↓ depression,
    │                  ↑ cognitive function
    │
    ├── IMMUNE: ↑ immune function (moderate exercise)
    │
    └── LONGEVITY: ↓ all-cause mortality, ↓ cancer risk

---

2. Sports Physiology - Definition and Importance

Definition

---

IMPORTANCE OF SPORTS PHYSIOLOGY

1. Performance optimization - understanding how muscles, heart, lungs work during exercise enables targeted training
2. Injury prevention - knowledge of musculoskeletal physiology helps prevent overuse injuries
3. Training program design - evidence-based interval training, resistance training, periodization
4. Nutrition guidance - carbohydrate loading, protein requirements, hydration strategies
5. Recovery strategies - understanding repair mechanisms, active recovery, sleep
6. Altitude adaptation - understanding acclimatization for mountain/altitude training
7. Ergogenic aids - scientific evaluation of supplements and performance enhancers
8. Rehabilitation - exercise prescription for injury recovery
9. Public health - prescribing exercise as medicine for chronic diseases
10. Doping control - understanding what is physiologically achievable vs artificial enhancement

---

3. Physiological Changes During Acute Exercise

Definition

---

CARDIOVASCULAR CHANGES

EXERCISE STARTS
      ↓
↑ Sympathetic activity; ↓ Vagal tone
      ↓
┌─────────────────────────────────┐
│ ↑ Heart Rate (from 70 → 180 bpm)│
│ ↑ Stroke Volume (70 → 110 mL)  │
│ ↑ Cardiac Output (5 → 20 L/min)│
│ ↑ Systolic BP                   │
│ Diastolic BP remains constant   │
│ ↑ Blood flow to muscles (20x)  │
│ ↓ Blood flow to viscera/skin    │
└─────────────────────────────────┘

---

RESPIRATORY CHANGES

---

METABOLIC CHANGES

ENERGY SYSTEMS ACTIVATED IN ORDER:
0-10 seconds: ATP-PCr system (phosphocreatine)
10-90 seconds: Anaerobic glycolysis (lactic acid produced)
>2 minutes: Aerobic oxidation (O₂-dependent)

O₂ DEBT/EXCESS POST-EXERCISE O₂ CONSUMPTION (EPOC):
Exercise → O₂ demand exceeds supply → O₂ deficit
After exercise → O₂ consumption remains elevated → replenishes stores

---

OTHER CHANGES

---

4. Respiratory Changes During Exercise and Their Significance

MECHANISMS DRIVING INCREASED VENTILATION DURING EXERCISE

EXERCISE
    │
    ├── NEURAL FACTORS (FAST - immediate onset):
    │     - Cortical irradiation from motor cortex
    │     - Proprioceptive input from joints/muscles
    │     - Anticipatory rise even before exercise starts
    │
    └── CHEMICAL FACTORS (SLOWER - sustaining response):
          - ↑ CO₂ production → ↑ PCO₂ → stimulates chemoreceptors
          - ↑ H⁺ (lactic acid at high intensity) → stimulates peripheral chemoreceptors
          - ↑ body temperature → stimulates respiratory centers
          - ↑ K⁺ from muscle → peripheral chemoreceptors

---

VENTILATORY THRESHOLD (ANAEROBIC THRESHOLD)

EXERCISE INTENSITY (low) → Aerobic metabolism → normal VE/VO₂ ratio

EXERCISE INTENSITY > ~60% VO₂max (untrained):
      ↓
Anaerobic threshold reached
      ↓
Lactic acid accumulates → ↑ H⁺
      ↓
DISPROPORTIONATE ↑ in ventilation (hyperventilation)
      ↓
Ventilatory Threshold (VT) detected on gas exchange tests
(used to determine training intensity)

---

RESPIRATORY CHANGES DURING EXERCISE

---

SIGNIFICANCE OF RESPIRATORY CHANGES

1. Maintain O₂ supply to working muscles
2. Remove CO₂ produced by increased metabolism
3. Regulate acid-base balance - buffer lactic acid by blowing off CO₂
4. Thermoregulation - evaporative water loss from lungs
5. Training effect - regular exercise improves respiratory muscle endurance, increases lung efficiency
6. VO₂ max - most important determinant of aerobic fitness; trainable
7. Ventilatory threshold - reliable predictor of endurance performance

---

QUICK REFERENCE: KEY VALUES TO REMEMBER

---

---

Exam Tips:

• Every 10-mark answer should have: Definition + Diagram + Classification/Types + Functions + Summary table
• Draw diagrams neatly with labels - they carry 2-3 marks
• Use flowcharts for mechanisms (coagulation, erythropoiesis, urine formation)
• Use comparison tables (arteries vs veins, mitosis vs meiosis) for easy marks
• Always write the correct units and normal values when relevant
• Conclude with a short clinical significance or application sentence