Anatomy & Physiology
Anatomy & Physiology Overview
Session 1: Cells and Tissue Levels of Organizations
Levels of organization: Cells ➔ Tissues ➔ Organs ➔ Organ Systems.
Cells: The basic unit of construction for all living things. They are the smallest units capable of performing life functions, containing organelles that carry out specific tasks.
Tissues: Groups of cells with similar structure or function, classified into four major types: epithelial, connective, muscle, and nervous tissues.
Organs: Composed of two or more types of tissues performing specific functions; for example, the heart is made of muscle tissue (to pump blood), connective tissue (for support), and nerve tissue (to regulate heartbeats).
Organ Systems: Groups of organs and tissues working together to perform complex functions; for instance, the cardiovascular system includes the heart, blood, and blood vessels.
Major Features of the Cell
Cytoplasm: A jelly-like fluid where cell components, including organelles, are suspended. It facilitates the movement of materials in the cell.
Nucleus: Contains genetic material (DNA/RNA) and regulates activities such as cell growth, metabolism, and reproduction.
Mitosis: The process of cell division that allows for growth, repair, and reproduction by producing two identical daughter cells.
Structure of a Generalized Cell
Components include:
Golgi apparatus: Modifies, sorts, and packages proteins for secretion or delivery to other organelles.
Plasma membrane: A phospholipid bilayer that acts as a semi-permeable barrier, controlling the movement of substances in and out of the cell.
Lysosome: Contains digestive enzymes to break down waste, cellular debris, and macromolecules.
Nucleus: The largest organelle, containing DNA organized into chromosomes.
Centrioles: Cylindrical structures involved in cell division, helping to organize the mitotic spindle.
Cytoplasm: Not just a fluid; it also contains cytosol and organelles functioning to maintain cellular processes.
Nucleolus: A small, dense structure within the nucleus where ribosomal RNA is produced.
Endoplasmic reticulum (ER): A network of membranes involved in protein and lipid synthesis; Rough ER is studded with ribosomes for protein transport, while Smooth ER synthesizes lipids and detoxifies certain chemicals.
Mitochondria: Known as the powerhouse of the cell, converting glucose and oxygen into ATP (adenosine triphosphate) through cellular respiration. They have their own DNA, indicating they were once free-living organisms.
Ribosomes: Small structures where protein synthesis occurs, either freely floating in the cytoplasm or attached to the rough ER.
Plasma Membrane
Composition: A phospholipid bilayer composed of hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails, providing a flexible structure and fluidity.
Function: Acts as a semi-permeable barrier, allowing only certain substances to pass and maintaining the internal environment of the cell.
Types of Cells
Different types include:
Epithelial cells: Form protective layers and are involved in absorption, secretion, and sensation.
Muscle cells: Specialized for contraction and movement; types include skeletal, cardiac, and smooth muscle cells.
Nerve cells (neurons): Transmit electrical signals throughout the body, playing critical roles in communication and coordination.
Connective tissue cells: Provide support, binding other tissues together; includes types such as fibroblasts and adipocytes (fat cells).
Nucleus
Description: An oval or spherical body, the largest structure in a cell, acting as the control center.
Function: Surrounded by a nuclear envelope with pores for transport, houses chromatin (DNA and associated proteins) which condenses to form chromosomes during cell division. It orchestrates cell activities by regulating gene expression.
Endoplasmic Reticulum (ER)
Types: Rough ER (with ribosomes for protein transport to specific destinations in the cell) and Smooth ER (responsible for lipid synthesis and detoxification processes). It plays a crucial role in nutrient processing and calcium storage.
Mitochondria
Function: Generate and store energy through the conversion of glucose into ATP via oxidative phosphorylation in the inner membrane.
Types of cellular respiration:
Aerobic: Requires oxygen for high-yield ATP production.
Anaerobic: Occurs when oxygen is limited, resulting in lower ATP yield and byproducts like lactic acid.
Golgi Apparatus
Function: Modifies, sorts, and packages proteins synthesized in the rough ER into vesicles for transport to their destinations or secretion from the cell.
Lysosomes
Function: Contain hydrolytic enzymes that break down organelles, biomolecules, and foreign materials, playing a key role in cellular digestion and waste disposal.
Cell Physiology: Diffusion and Osmosis
Diffusion (Passive): The net movement of solutes from an area of high concentration to an area of low concentration until equilibrium is achieved. Examples include gas exchange in the lungs.
Facilitated diffusion: Requires specific transporter proteins to facilitate the movement of larger, non-lipid soluble molecules across the plasma membrane.
Osmosis (Passive): The movement of water molecules through a selectively permeable membrane from an area of high water concentration (low solute) to low water concentration (high solute).
Types of Solutions
Hypotonic: Contains lower solute concentration than the cellular cytoplasm causing cells to swell as water enters.
Hypertonic: Contains higher solute concentration than the cellular cytoplasm, leading to cell shrinkage as water exits.
Isotonic: Has the same solute concentration as the cell, maintaining cell size and shape as there is no net movement of water.
Cell Ingestion Mechanisms
Pinocytosis: Also known as cell drinking; involves the uptake of extracellular fluid and dissolved substances.
Phagocytosis: Known as cell eating; the process of engulfing solid particles and microorganisms, crucial for immunological defense.
Classification of Tissues
Four fundamental tissue types:
Connective tissue: Provides structural support, protection, and transportation (includes blood, bone, cartilage, and adipose tissues).
Cell types include:
Fibroblasts: Produce extracellular matrix components.
Macrophages: Involved in immune response and phagocytosis.
Epithelial Tissue: Characterized by tightly packed cells; can be simple (single layer) or stratified (multiple layers), forming barriers and facilitating absorption.
Muscle Tissue: Responsible for movement; categorized into:
Skeletal (voluntary, striated muscles controlled consciously).
Smooth (involuntary, non-striated muscles, found in walls of hollow organs).
Cardiac (involuntary, striated muscles making up the heart, characterized by intercalated discs for synchronized contractions).
Nervous Tissue: Specializes in the transmission of electrical impulses throughout the body, comprising neurons and glial cells which support neuron function.
The Cardiovascular System
Anatomy of the Heart
Position: Located in the mediastinum, approximately two-thirds to the left of the midline, protected by the rib cage.
Chambers:
Right atrium: Receives deoxygenated blood from the superior and inferior vena cava.
Right ventricle: Pumps deoxygenated blood to the lungs via the pulmonary arteries for oxygenation.
Left atrium: Receives oxygenated blood from the lungs through pulmonary veins.
Left ventricle: Pumps oxygenated blood to the rest of the body through the aorta.
Valves:
Tricuspid valve: Between right atrium and right ventricle.
Bicuspid (mitral) valve: Between left atrium and left ventricle.
Pulmonary valve: Between right ventricle and pulmonary arteries.
Aortic valve: Between left ventricle and aorta.
Structure of the Heart
Wall Layers:
Epicardium (outer layer) provides a protective layer and is involved in heart lubrication.
Myocardium (middle layer) is the heart muscle responsible for contraction, comprising 95% of the heart’s mass. It is involuntary and contains specialized cardiac muscle cells.
Endocardium (inner layer) lining the heart chambers and covering the valves, preventing blood clotting.
Heart Muscle: Cardiac muscle fiber has unique properties, including rhythmic contraction and the presence of intercalated discs that facilitate the synchronized contraction of heart cells.
Blood Flow Pathways
Pulmonary Circulation: Involves the flow of deoxygenated blood from the right atrium ➔ right ventricle ➔ pulmonary arteries ➔ lungs for gas exchange, where carbon dioxide is expelled, and oxygen is absorbed.
Coronary Circulation: Supplies blood to the heart muscle (myocardium) via the right and left coronary arteries, crucial for maintaining heart function.
Blood Pressure and Cardiac Output
Blood Pressure (BP): The force exerted by circulating blood on the walls of blood vessels, measured as systolic (pressure during heartbeats) over diastolic (pressure during resting phase) values.
Factors influencing BP: Include cardiac output (the amount of blood the heart pumps), peripheral resistance (the resistance of blood vessels), and overall blood volume (total amount of blood in circulation).
Hormonal Control in the Body
Endocrine System: A network of secretory glands that release hormones into the bloodstream, influencing various body functions such as metabolism, growth, and mood regulation.
Hypothalamus: A critical brain region that links the nervous system with the endocrine system, regulating homeostasis.
Key Hormones Produced:
Insulin (from pancreas): Regulates blood sugar levels, facilitating glucose uptake into cells.
Type 1 diabetes: Characterized by no insulin production due to autoimmune destruction of pancreatic beta cells.
Type 2 diabetes: Involves insulin resistance, where cells do not respond effectively to insulin.
Calcitonin (from thyroid gland): Decreases blood calcium levels, acting to lower risks of hypercalcemia; it operates against parathyroid hormone (PTH).
Parathyroid Hormone (PTH): Increases blood calcium levels through mechanisms like reabsorption from bones, enhancement of calcium reabsorption in kidneys, and increased intestinal calcium absorption.
Immune System Surveillance
Types of Immunity:
Innate immunity: Provides immediate, non-specific responses to pathogens using physical barriers (skin, mucous membranes) and cellular responses.
Adaptive immunity: Involves specific, learned responses to particular pathogens, which develop over time and through exposure.
Immune Cells:
White blood cells (leukocytes): Include B cells (produce antibodies) and T cells (destroy infected cells) that play major roles in the immune defense against pathogens.
Inflammatory Response: Involves a sequence of events including vasodilation (widening of blood vessels), increased capillary permeability, and recruitment of immune cells (like neutrophils and macrophages) to the site of infection or injury.
Vaccination and Antibody Production
Adaptive immunity development: Upon initial exposure to pathogens, the immune system creates memory cells, enabling faster responses to future infections by the same pathogen.
B cells transform into plasma cells: After activation by antigens, they produce antibodies that neutralize specific antigens, such as viruses and bacteria.
Nervous System Overview
Central Nervous System (CNS): Comprises the brain and spinal cord, integrating sensory information, and coordinating responses and functions throughout the body.
Peripheral Nervous System (PNS): Comprises cranial and spinal nerves, responsible for communication between the CNS and the rest of the body, facilitating both motor and sensory functions.
Structure of the Kidneys
Functions: Involved in the excretion of waste products, regulation of blood pressure, management of electrolyte balance, and erythropoiesis (production of red blood cells).
Nephrons: The functional units of the kidney, filtering blood and forming urine through a series of processes that include filtration, reabsorption, and secretion.
Urinary System Components:
Ureters: Tubes that convey urine from the kidneys to the bladder, facilitating urine storage.
Bladder: A muscular reservoir for urine, expandable to accommodate varying volumes, with stretch receptors signalling fullness.
Urethra: The tube conducting urine from the bladder to the exterior, varying in length between males and females.
Pathologies Related to the Urinary System
Common Conditions:
Glomerulonephritis: Inflammation of the tiny filters (glomeruli) in the kidneys, affecting their filtering ability.
Nephrolithiasis (kidney stones): Hard mineral deposits form in the kidneys, potentially causing severe pain and urine flow obstruction.
Renal failure: The kidneys lose their ability to filter waste from the blood effectively. This can be acute or chronic, leading to toxin build-up and requiring treatment such as dialysis or transplantation