Cardiovascular System: The Heart and Blood Vessels

Heart Anatomy

The heart is a muscular organ responsible for pumping blood throughout the body. It is divided into four chambers: two atria and two ventricles.

• Pericardium: A double-walled sac that surrounds and protects the heart, consisting of the fibrous and serous pericardium.

• Systemic vs. Pulmonary Circuits: The systemic circuit carries oxygenated blood from the left side of the heart to the body, while the pulmonary circuit carries deoxygenated blood from the right side of the heart to the lungs for oxygenation.

Blood Vessels: Structure and Function

Blood vessels transport blood throughout the body and are classified as arteries, veins, and capillaries.

• Arteries: Carry blood away from the heart; have thick, elastic walls to withstand high pressure.

• Veins: Return blood to the heart; have thinner walls and valves to prevent backflow.

• Capillaries: Microscopic vessels where exchange of gases, nutrients, and wastes occurs between blood and tissues.

ECG and Cardiac Cycle

The electrocardiogram (ECG) records the electrical activity of the heart. The cardiac cycle consists of alternating periods of contraction (systole) and relaxation (diastole).

• Systole: Contraction phase; blood is ejected from the chambers.

• Diastole: Relaxation phase; chambers fill with blood.

• Baroreceptors: Detect changes in blood pressure and help regulate heart rate.

• Chemoreceptors: Detect changes in blood chemistry (e.g., CO2, O2) and influence cardiac and respiratory function.

Autorhythmic/Intrinsic Conduction System

The heart's intrinsic conduction system coordinates contraction through specialized cardiac muscle cells.

• Sinoatrial (SA) Node: The pacemaker; initiates electrical impulses.

• Atrioventricular (AV) Node: Delays impulse before passing to ventricles.

• Bundle of His, Bundle Branches, Purkinje Fibers: Distribute impulses through ventricles, ensuring coordinated contraction.

Autonomic Regulation of the Heart

• Parasympathetic Nervous System: Decreases heart rate and promotes rest-and-digest activities.

• Sympathetic Nervous System: Increases heart rate and force of contraction, preparing the body for 'fight or flight.'

• Homeostasis: Balance between sympathetic and parasympathetic input maintains stable internal conditions.

The Lymphatic System and Immunity

Components and Functions

The lymphatic system returns excess tissue fluid to the bloodstream and plays a key role in immune defense.

• Lymph: Fluid transported by lymphatic vessels.

• Lymphatic Vessels: Network that returns lymph to the circulatory system.

• Lymph Nodes: Filter lymph and house lymphocytes.

• Spleen, Thymus, Tonsils: Organs involved in immune responses and lymphocyte maturation.

Innate vs. Adaptive Immunity

Lymphatic and Immune Dysfunction

• Lymphedema: Swelling due to lymph accumulation.

• Immunodeficiency: Impaired immune response (e.g., HIV/AIDS).

• Autoimmune Disorders: Immune system attacks self-tissues (e.g., lupus).

T-cell and B-cell Mediated Immunity

• T-cell Immunity (Cell-mediated): T cells recognize and destroy infected or abnormal cells.

• B-cell Immunity (Humoral): B cells produce antibodies that neutralize pathogens.

• Steps: Antigen presentation → Lymphocyte activation → Proliferation and differentiation → Effector response.

The Respiratory System

Components and Functions

• Upper Respiratory Tract: Nose, nasal cavity, pharynx, larynx; filters, warms, and moistens air.

• Lower Respiratory Tract: Trachea, bronchi, bronchioles, lungs; conducts air to gas exchange surfaces.

Mechanics of Pulmonary Ventilation

Ventilation is the movement of air into and out of the lungs, driven by pressure changes.

• Inhalation: Diaphragm and external intercostals contract, increasing thoracic volume and decreasing pressure.

• Exhalation: Muscles relax, thoracic volume decreases, pressure increases, air flows out.

Respiratory Muscles

• Diaphragm: Main muscle of inspiration.

• External Intercostals: Elevate ribs during inspiration.

• Internal Intercostals, Abdominal Muscles: Assist in forced expiration.

Gas Exchange and Transport

• External Respiration: Exchange of O2 and CO2 between alveoli and blood.

• Internal Respiration: Exchange of gases between blood and tissues.

• Oxygen Transport: Mostly bound to hemoglobin; some dissolved in plasma.

• Carbon Dioxide Transport: Dissolved in plasma, bound to hemoglobin, or as bicarbonate ions ().

Neural Control of Respiration

• Medullary Respiratory Centers: Control basic rhythm of breathing.

• Pontine Centers: Modify breathing pattern.

Pulmonary Disease and Smoking

• Obstructive Diseases: (e.g., asthma, COPD) Narrow airways, reduce airflow.

• Restrictive Diseases: (e.g., fibrosis) Decrease lung compliance.

• Smoking: Damages cilia, increases risk of cancer, emphysema, and chronic bronchitis.

The Digestive System

Functional Anatomy

• Major Organs: Mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus.

• Accessory Organs: Salivary glands, liver, gallbladder, pancreas.

Major Digestive Hormones

Digestion and Absorption

• Physical Digestion: Mechanical breakdown (chewing, churning).

• Chemical Digestion: Enzymatic breakdown of macromolecules.

• Absorption: Nutrients absorbed mainly in the small intestine.

Control of Digestive Activities

• Hormonal Control: Hormones regulate secretion and motility.

• Neural Reflexes: Enteric nervous system and autonomic input coordinate digestive processes.

Digestive System Dysfunction

• Ulcers: Erosion of stomach or duodenal lining.

• Malabsorption: Impaired nutrient absorption (e.g., celiac disease).

• Inflammatory Disorders: (e.g., Crohn's disease, ulcerative colitis).

Metabolism and Energetics

Key Definitions

• Metabolism: All chemical reactions in the body.

• Catabolism: Breakdown of molecules to release energy.

• Anabolism: Synthesis of complex molecules from simpler ones.

• Cellular Respiration: Process of generating ATP from nutrients.

• Aerobic vs. Anaerobic: Aerobic requires oxygen; anaerobic does not.

• Glycolysis: Anaerobic breakdown of glucose to pyruvate.

• Pyruvate: End product of glycolysis; enters mitochondria for aerobic respiration or is converted to lactate anaerobically.

• Gluconeogenesis: Formation of glucose from non-carbohydrate sources.

• Glycogen: Storage form of glucose in liver and muscles.

The Urinary System and Fluid, Electrolyte, and Acid-Base Balance

Functional Anatomy

• Organs: Kidneys, ureters, urinary bladder, urethra.

• Kidneys: Filter blood, regulate fluid and electrolyte balance, and remove wastes.

Nephron Structure and Function

• Nephron: Functional unit of the kidney; consists of renal corpuscle (glomerulus + Bowman's capsule) and renal tubule (proximal tubule, loop of Henle, distal tubule, collecting duct).

• Glomerular Filtration: Blood pressure forces water and solutes from glomerulus into Bowman's capsule.

• Reabsorption: Movement of substances from filtrate back into blood.

• Secretion: Transfer of additional wastes from blood into filtrate.

Hormonal Influence on Urine and Blood Pressure

• Antidiuretic Hormone (ADH): Increases water reabsorption, concentrates urine.

• Aldosterone: Increases sodium reabsorption, affects blood volume and pressure.

• Atrial Natriuretic Peptide (ANP): Reduces sodium reabsorption, lowers blood pressure.

The Reproductive System

Functional Anatomy

• Male Organs: Testes, epididymis, vas deferens, seminal vesicles, prostate, penis.

• Female Organs: Ovaries, uterine tubes, uterus, vagina, external genitalia.

Female Reproductive Cycle

• Ovarian Cycle: Follicular phase (follicle growth), ovulation (release of oocyte), luteal phase (corpus luteum activity).

• Uterine Cycle: Menstrual phase (shedding of endometrium), proliferative phase (regrowth), secretory phase (preparation for implantation).

• Hormonal Regulation: Involves GnRH, FSH, LH, estrogen, and progesterone.

• Connections: Ovarian hormones regulate uterine cycle; feedback loops control hormone release.