Human Anatomy and Physiology

Summary of Syllabus

• Structure relates to physiology of important functions and processes within the mammalian body.
• Focuses on:
  • Cells and tissues in mammals.
  • Relations of tissue structure to functions.
  • Major organ systems including:
  • Digestive system
  • Respiratory system
  • Cardiovascular system
  • Immune system
  • Musculoskeletal system
• Discussion of associated malfunctioning of these systems.

Tissues - Definition and Classification

• Tissues: A collection of similar cells performing a specific role in structuring and functioning the body.
• Histology: The study of tissues.
• Cells in tissues are separated and bound by a non-living intercellular matrix, secreted by the cells, which varies in composition across different tissues (liquid, semi-solid, solid).

Examples of Matrix Composition

• Blood: Liquid matrix allows tissue to flow through vessels.
• Bone: Solid matrix provides structural support.

Four Main Tissue Groups

1. Epithelial Tissues:
   • Cover body and organ surfaces.
   • Line body cavities and lumina.
   • Form glands.
2. Muscular Tissues:
   • Contract to enable movement.
3. Connective Tissues:
   • Include blood, cartilage, bone, and connective tissue proper.
4. Nervous Tissues:
   • Transmit impulses throughout the body.

Characteristics Common to All Epithelia

1. Composed almost entirely of cells with minimal intercellular material.
2. Covers the body surface and lines cavities, vessels, and forms glands (e.g. salivary glands).
3. Most have a free surface not associated with other cells and a basal surface attached to a basement membrane.
   • Some epithelia (e.g. endocrine glands) may lack a free surface.
4. Specialized cell contacts (tight junctions, desmosomes) bind adjacent cells.
5. Blood vessels do not penetrate the basement membrane, thus nutrients and gases diffuse across from underlying connective tissues.
6. Innervation: Epithelia are supplied by nerve fibers despite being avascular.
7. Regeneration: Epithelial cells can undergo mitosis to replace damaged cells.
   • Regeneration is essential due to exposure to friction or hostile substances, allowing replacement by cell division.

Classification of Epithelium

• Two Major Categories:
  • Membranous Epithelia: Line all body surfaces and cavities; specialized for protection and absorption.
  • Glandular Epithelia: Specialized for secretion.

Characteristics of Membranous Epithelia

• Line surfaces of the body, within cavities and tubes.
• Derived from three germ layers:
  • Ectoderm: e.g., skin's outer layer.
  • Mesoderm: e.g., lining of blood vessels.
  • Endoderm: e.g., lining gastrointestinal tract.

Functions of Membranous Epithelia

1. Provide protection from pathogens.
2. Absorb products of digestion (e.g., lining of the GIT).
3. Facilitate filtration (e.g., in the kidneys).
4. Allow for diffusion (e.g., in the lungs' air sacs).
5. Contain specialized neuro-epithelial cells serving as chemoreceptors.

Classification by Number of Cell Layers and Shape

• Simple Columnar Epithelium:
  • Composed of tall columnar cells, some containing cilia (e.g., in the digestive tract).
  • Goblet cells secrete mucus for protection.
• Stratified Squamous Epithelium:
  • Contains multiple cell layers; protective, with keratinized (skin) and non-keratinized types (mouth).
• Pseudostratified Ciliated Columnar Epithelium:
  • Appears stratified but is a single layer, typically in respiratory systems.
• Transitional Epithelium:
  • Unique to the urinary bladder; specialized for distension.

Body Membranes

• Composed of epithelial tissues that cover, separate and support organs, lining cavities.
• Types:
  • Mucous Membranes: Secrete mucus to protect organs (e.g., respiratory tract).
  • Serous Membranes: Line thoracic and abdominal cavities, secrete serous fluid for lubrication; includes:
  • Pleurae: around lungs.
  • Pericardial membrane: around heart.
  • Peritoneal membranes: in abdominal cavity.

Glandular Epithelium

• Specialized for secretion, composed of epithelium and connective tissue.
• Exocrine Glands: Have ducts; secrete enzymes, etc.
• Endocrine Glands: No ducts; secrete hormones directly into the bloodstream.
• Classification by:
  • Number of cells (unicellular vs. multicellular).
  • Structure of ducts (simple vs. compound).

Modes of Secretion

1. Merocrine Glands: Secretion without loss of cellular material (e.g., sweat glands).
2. Apocrine Glands: Fragments of gland cells released (e.g., mammary glands).
3. Holocrine Glands: Entire cells shed in secretion (e.g., sebaceous glands).

Connective Tissues

• Definition: Consists of cells separated by extracellular matrix.
• Highly vascular except mature cartilage; responsible for organ repair.
• Connective tissue classification based on three components:
  • Protein Fibres: Collagen, reticular, elastic.
  • Collagen: Most common protein, strong and flexible, coiled in structure.
  • Ground Substance: Non-fibrous proteins and molecules, influencing tissue properties.
  • Fluid: Varies in volume and function.

Embryonic Connective Tissues

• Mesenchyme: Undifferentiated connective tissue present early in development.

Connective Tissue Proper Types

1. Loose (Areolar): Binds skin to muscles, supports blood vessels.
2. Dense Regular: Strong, flexible (tendons, ligaments).
3. Dense Irregular: Provides tensile strength (dermis of skin).
4. Elastic: Contains elastic fibers (found in large arteries).
5. Reticular: Networked fibres supporting organ structures (liver, spleen).
6. Adipose Tissue: Stores fat, cushions organs.

Cartilage

• Composed of chondrocytes in a semi-solid matrix.
• Types include:
  1. Hyaline Cartilage: Forms structures (e.g., joints); most common.
  2. Fibrocartilage: Strong, withstands tension (e.g., between vertebrae).
  3. Elastic Cartilage: Flexible and resilient (e.g., in outer ear).

Bone Tissue (Osseous Connective Tissue)

• Most rigid connective tissue; contains calcium phosphate for hardness.
• Two types:
  • Compact Bone: Dense outer layer.
  • Spongy Bone: Lighter interior containing marrow.

Muscle Tissues

• Function primarily for movement; derived from mesoderm.
• Three main types:
  1. Skeletal Muscle: Voluntary control; attached to skeleton.
  2. Smooth Muscle: Involuntary control; found in hollow organs.
  3. Cardiac Muscle: Involuntary control; found in the heart.

Nervous Tissue

• Composed of neurons and supportive cells (neuroglia).
• Neurons: Carry electrical impulses; consist of cell body, dendrites, axon.
• Neuroglia: Support neurons; participate in metabolic functions.

Digestive System

• Anatomically and functionally divided into:
  • Gastrointestinal (GI) Tract: Tubular structure (mouth to anus).
  • Accessory Organs: Teeth, saliva glands, liver, pancreas, gallbladder.
• Functions:
  1. Motility: Movement of food (ingestion, swallowing, peristalsis).
  2. Secretion: Enzymatic and hormonal secretions.
  3. Digestion: Breakdown of complex molecules.
  4. Absorption: Nutrient uptake into blood or lymph.

Layers of the GIT

• Composed of four layers (tunics):
  1. Mucosa: Absorptive/secretory layer.
  2. Submucosa: Vascular and glandular supportive layer.
  3. Muscularis: Responsible for peristalsis (movement).
  4. Serosa: Protective outer layer.

Mouth, Pharynx, and Associated Structures

• Mouth: Initiates mechanical digestion; formed by cheeks, lips, palate, tongue.
• Pharynx: Connects the mouth and nasal cavities to the trachea and esophagus; allows air and food passage.
• Salivary Glands: Produce saliva containing enzymes for food digestion.
• Tongue: Assists in chewing and swallowing, contains taste buds and muscles.
• Pharynx's Regions:
  • Nasopharynx: Respiratory function only.
  • Oropharynx: Shared respiratory and digestive functions.
  • Laryngopharynx: Directs food into the esophagus and air into the larynx.

Oesophagus and Stomach

• Oesophagus: Muscular tube connecting pharynx to stomach, lined with stratified squamous epithelium.
• Stomach: Stores food, initiates protein digestion, and converts food to chyme. Divided into four regions (fundus, body, pylorus) and has gastric rugae for surface area.
  • Gastric Glands: Secrete components like mucus (goblet cells), HCl (parietal cells), pepsinogen (chief cells), and intrinsic factor for vitamin B12 absorption.

Small Intestine

• Comprises duodenum, jejunum, and ileum; specialized for absorption through villi and microvilli.
• Receives bile and pancreatic juice for further digestion; absorption of nutrients occurs here.

Large Intestine

• Absorbs water and electrolytes, forming stored feces. Regions include the cecum, colon, rectum, and anus.

Circulatory System

• Components: Cardiovascular system (blood, heart, vessels) and lymphatic system (lymph and lymph nodes).
• Function: Transports oxygen, nutrients, hormones; involved in immune response.
• Blood: Composed of plasma and formed elements (RBCs, WBCs, platelets), with RBCs transporting oxygen via hemoglobin.

Heart Structure and Function

• Composed of epicardium, myocardium, endocardium.
• Contains four chambers: atria and ventricles, with valves ensuring unidirectional blood flow.
• Works through the cardiac cycle of contraction (systole) and relaxation (diastole).