ANATOMY STUDY UNIT 1.1-1.2

STUDY UNIT $1.1$: HUMAN TISSUE

$1$. EPITHELIAL TISSUE

A tissue is a group of similar cells and their products performing a specialized function. Epithelial tissue serves as a boundary between different environments.

$1.1$ Special Characteristics

• Cellularity: Consists almost entirely of tightly packed cells with minimal extracellular material.

• Polarity: Always has an apical surface (free/exposed) and a basal surface (attached to underlying tissue).

• Basement Membrane: A thin layer that anchors the epithelium to the underlying connective tissue, providing structural support.

• Avascular but Innervated: Contains no blood vessels (receives nutrients via diffusion from the dermis) but is supplied by nerve fibers.

• Regeneration: High mitotic rate allows for quick replacement of damaged or lost cells.

$1.2$ Classification & Locations

• Simple Squamous: Single flat layer; facilitates diffusion (e.g., Alveoli, Capillaries).

• Stratified Squamous: Multiple layers; protects against abrasion (e.g., Epidermis, Mouth, Esophagus).

• Simple Cuboidal: Cube-shaped; specialized for secretion and absorption (e.g., Kidney tubules, Glands).

• Simple Columnar: Tall cells; often contains microvilli for absorption (e.g., Stomach, Intestines).

• Pseudostratified Ciliated Columnar: Single layer appearing stratified; contains cilia to move mucus (e.g., Trachea).

• Transitional: Cells change shape to allow stretching (e.g., Urinary bladder).

$2$. CONNECTIVE TISSUE

Connective tissue is characterized by its Extracellular Matrix ($ECM$), which consists of ground substance and fibers (collagen, elastic, and reticular).

• Loose Connective: includes Areolar (cushioning) and Adipose (fat storage, insulation).

• Dense Connective: Includes Tendons (muscle to bone) and Ligaments (bone to bone).

• Supporting Connective: Bone (calcified matrix for support) and Cartilage (flexible support).

• Fluid Connective: Blood and Lymph, used for transport.

$3$. MUSCLE TISSUE

Specialized for contraction and movement:

• Skeletal: Striated, multinucleated, and voluntary; attached to the skeleton.

• Cardiac: Striated, branched, involuntary, with intercalated discs for synchronized beating; found in the heart.

• Smooth: Spindle-shaped, non-striated, and involuntary; found in hollow organs (e.g., gut, uterus, blood vessels).

$4$. NERVOUS TISSUE

Responsible for internal communication.

• Neurons: Specialized cells that ga,enerate and conduct electrical impulses.

• Neuroglia: Non-conducting cells that provide physical support, insulation, and nutrients to neurons.

$5$. BODY MEMBRANES

• Cutaneous: The skin; a dry, keratinized membrane.

• Mucous (Mucosae): Wet membranes lining cavities open to the exterior; often secrete mucus for lubrication.

• Serous (Serosae): Double-layered membranes (Parietal and Visceral) lining closed cavities; they secrete serous fluid to reduce friction (e.g., Pleura, Pericardium).

STUDY UNIT $1.2$: INTEGUMENTARY SYSTEM

$1$. FUNCTIONS OF THE SKIN

• Protection: Chemical (acid mantle), Physical (keratin barrier), and Biological (immune cells).

• Thermoregulation: Sweat evaporation and blood vessel constriction/dilation.

• Sensation: Detection of touch, pressure, temperature, and pain.

• Metabolism: Synthesis of Vitamin D from sunlight.

• Excretion: Removal of nitrogenous wastes through sweat.

$2$. SKIN STRUCTURE

• Epidermis: The superficial layer made of keratinized stratified squamous epithelium. It provides a waterproof barrier.

• Dermis: The thick, fibrous layer containing collagen, elastic fibers, blood vessels, and sensory receptors.

• Hypodermis: The subcutaneous layer comprised of adipose tissue; it anchors skin and provides insulation.

$3$. GLANDULAR FUNCTIONS

• Eccrine Sweat Glands: Coiled glands that discharge sweat directly onto the skin surface to lower body temperature.

• Apocrine Sweat Glands: Located in axillary and anogenital areas; they secrete a thicker fluid in response to stress or hormonal triggers.

• Sebaceous Glands: Produce sebum (oil) to lubricate skin and hair and inhibit bacterial growth.

$4$. ABDOMINAL LANDMARKS

• Costal Margin: The lower edge of the rib cage ($7^{th}$-$10^{th}$ ribs).

• Iliac Crest: The superior border of the hip bone.

• Linea Alba: A white fibrous line marking the midline of the abdomen.

• Mid-clavicular Line: A vertical reference line starting at the center of the clavicle.

$5$. WOUND HEALING PHASES

1. Inflammatory Phase: Clotting occurs and white blood cells migrate to the area to clear debris.

2. Proliferative Phase: Fibroblasts deposit new collagen, and granulation tissue forms.

3. Maturation Phase: The scar is remodeled and strengthened over time.

Microscopic Anatomy of Compact Bone

1. Compact bone is composed of structural units called osteons (Haversian systems).

2. Each osteon contains a central (Haversian) canal running longitudinally through the bone.

3. The central canal contains blood vessels, nerves, and lymphatic vessels.

4. Surrounding the central canal are concentric rings called lamellae.

5. Lamellae consist of collagen fibres and mineral salts arranged in alternating directions, providing strength.

6. Lacunae are small spaces located between the lamellae.

7. Lacunae house osteocytes, the mature bone cells responsible for maintaining bone tissue.

8. Canaliculi are microscopic channels that connect lacunae to each other and to the central canal.

9. Canaliculi allow diffusion of nutrients, oxygen, and waste products between osteocytes.

10. Volkmann’s (perforating) canals run perpendicular to osteons and connect blood vessels between osteons and the periosteum.