Anatomy & Physiology Study Guide: Endocrine, Cardiovascular, Immune, Blood, and Respiratory Systems

Endocrine System

Overview of the Endocrine System

The endocrine system is a network of glands that secrete hormones to regulate various bodily functions, including metabolism, growth, reproduction, and stress responses. It works closely with the nervous system to maintain homeostasis.

• Hormones: Chemical messengers produced by endocrine glands, transported via the bloodstream to target organs.

• Lipid-based (steroid) hormones: Pass through cell membranes and bind to intracellular receptors, directly influencing gene expression.

• Amino acid-based (peptide) hormones: Bind to extracellular receptors on cell membranes, triggering secondary messenger pathways.

Example: Cortisol (a steroid hormone) enters cells and alters gene transcription, while insulin (a peptide hormone) binds to cell surface receptors to regulate glucose uptake.

Major Endocrine Glands and Their Hormones

• Hypothalamus: Located in the brain; links the nervous and endocrine systems. Produces releasing and inhibiting hormones (e.g., TRH, CRH, GnRH, GHRH, somatostatin, dopamine) that control the pituitary gland.

• Pituitary Gland: The "master gland" with anterior (adenohypophysis) and posterior (neurohypophysis) lobes.

  • Anterior Pituitary: GH, TSH, ACTH, Prolactin, LH, FSH

  • Posterior Pituitary: ADH (vasopressin), Oxytocin

• Thyroid Gland: Butterfly-shaped in the neck; secretes thyroxine (T4), triiodothyronine (T3) for metabolism, and calcitonin for calcium regulation.

• Parathyroid Glands: Four small glands on the thyroid's posterior; secrete parathyroid hormone (PTH) to increase blood calcium.

• Adrenal Glands: Sit atop kidneys; cortex produces corticosteroids (cortisol, aldosterone, androgens), medulla produces epinephrine and norepinephrine.

• Pancreas: Islets of Langerhans secrete insulin (lowers blood glucose), glucagon (raises blood glucose), and somatostatin (inhibits both).

• Pineal Gland: Produces melatonin for sleep-wake cycles.

• Gonads: Ovaries (estrogen, progesterone), testes (testosterone) for reproductive function and secondary sex traits.

• Thymus: Produces thymosin for T-cell maturation (immune function).

Key Hormones and Their Functions

• ADH (Antidiuretic Hormone): Increases water reabsorption in kidneys, dilutes blood, increases fluid volume.

• Oxytocin: Stimulates uterine contractions and milk ejection.

• Growth Hormone (GH): Stimulates tissue growth.

• TSH (Thyroid-Stimulating Hormone): Stimulates thyroid hormone secretion.

• ACTH (Adrenocorticotropic Hormone): Stimulates adrenal cortex steroid secretion.

• Prolactin: Stimulates milk production.

• LH (Luteinizing Hormone): Stimulates ovulation and hormone secretion in ovaries/testes.

• FSH (Follicle-Stimulating Hormone): Stimulates gamete production and estrogen secretion.

• Insulin: Lowers blood glucose by promoting cellular uptake and glycogen storage.

• Glucagon: Raises blood glucose by promoting glycogen breakdown.

• Cortisol: Stress response, increases blood glucose, suppresses immune system.

• Aldosterone: Regulates sodium and potassium balance.

• Epinephrine/Norepinephrine: Fight-or-flight response, increase heart rate and blood pressure.

Endocrine Disorders

• Diabetes Insipidus (DI): Excessive urination due to ADH deficiency or kidney insensitivity.

• SIADH (Syndrome of Inappropriate ADH Secretion): Excess ADH causes fluid retention and hyponatremia.

• Hashimoto’s Disease: Autoimmune hypothyroidism.

• Graves’ Disease: Autoimmune hyperthyroidism; can cause thyroid storm.

• Congenital Hypothyroidism: Insufficient thyroid hormone in infants, leading to developmental issues.

• Anabolic Steroids: Synthetic steroids that promote muscle growth (anabolic = "to build up").

Cardiovascular System

Heart Structure and Blood Flow

The heart is a muscular organ divided into four chambers: right and left atria (upper), right and left ventricles (lower). Valves ensure unidirectional blood flow.

• Right Atrium: Receives deoxygenated blood from the body.

• Right Ventricle: Pumps deoxygenated blood to the lungs.

• Left Atrium: Receives oxygenated blood from the lungs.

• Left Ventricle: Pumps oxygenated blood to the body.

• Valves:

  • Tricuspid: Right atrium to right ventricle

  • Bicuspid (Mitral): Left atrium to left ventricle

  • Pulmonary Semilunar: Right ventricle to pulmonary artery

  • Aortic Semilunar: Left ventricle to aorta

• Septum: Interatrial (between atria), interventricular (between ventricles)

Blood Flow Sequence: Body → Right Atrium → Tricuspid Valve → Right Ventricle → Pulmonary Valve → Pulmonary Arteries → Lungs → Pulmonary Veins → Left Atrium → Mitral Valve → Left Ventricle → Aortic Valve → Aorta → Body

Coronary Circulation

• Right Coronary Artery: Feeds right ventricle, posterior interventricular septum, inferior heart.

• Left Coronary Artery: Feeds left ventricle (lateral/anterior walls), part of right ventricle, interventricular septum.

Electrical Conduction System

• Sinoatrial (SA) Node: Pacemaker; initiates atrial contraction (70–80 bpm).

• Atrioventricular (AV) Node: Delays impulse for ventricular filling (40–60 bpm).

• Bundle of His: Carries impulse to ventricles.

• Purkinje Fibers: Distribute impulse for ventricular contraction.

Normal Flow: SA Node → AV Node → Bundle of His → Bundle Branches → Purkinje Fibers

Autonomic Regulation of the Heart

• Sympathetic Nervous System: Increases heart rate and contractility (norepinephrine).

• Parasympathetic Nervous System: Decreases heart rate (acetylcholine via vagus nerve).

Cardiac Action Potential and Electrolytes

• Depolarization: Sodium influx makes cell positive.

• Repolarization: Potassium efflux returns cell to negative state.

• Calcium: Triggers muscle contraction.

• Refractory Periods: Absolute (no stimulus can trigger), Relative (strong stimulus can trigger early beat).

Electrocardiogram (ECG) Waves

• P wave: Atrial depolarization (contraction).

• QRS complex: Ventricular depolarization (contraction).

• T wave: Ventricular repolarization.

Cardiovascular Diseases

• Valvular Stenosis: Valve too narrow, restricts flow.

• Valvular Insufficiency: Valve too loose, allows backflow.

• Silent MI: Heart attack with subtle or no pain.

Blood and Blood Vessels

Blood Composition

• Plasma: Liquid matrix with proteins (albumin, fibrinogen, globulins).

• Formed Elements: Red blood cells (erythrocytes), white blood cells (leukocytes), platelets (thrombocytes).

Blood Cell Production

• Hematopoiesis: Formation of blood cells in red bone marrow (pelvis, sternum, vertebrae, long bones).

• Erythropoiesis: Production of red blood cells.

Blood Clotting

• Platelets adhere to injury site, form plug, release serotonin (vasoconstriction).

• Coagulation cascade (requires calcium and clotting factors):

  • Prothrombin (with vitamin K) → Thrombin

  • Thrombin converts fibrinogen → Fibrin (forms clot)

• Clot retracts, vessel heals.

Equation:

$\text{Prothrombin} \xrightarrow{\text{Thrombin}} \text{Fibrinogen} \rightarrow \text{Fibrin}$

Blood Vessel Structure and Types

• Tunica Interna: Innermost, squamous epithelium.

• Tunica Media: Middle, smooth muscle and elastic tissue.

• Tunica Externa: Outermost, fibrous tissue for support.

• Arteries: Carry blood away from heart, thick walls.

• Arterioles: Small arteries, regulate flow to capillaries.

• Capillaries: Site of exchange (O2, CO2, nutrients, waste).

• Venules: Collect blood from capillaries.

• Veins: Return blood to heart, have valves.

• Vascular Shunt: Direct connection between arteriole and venule.

Blood Pressure and Hypertension Stages

Stage	Systolic (mmHg)	Diastolic (mmHg)
Normal	< 120	< 80
Elevated	120–129	< 80
Stage 1	130–139	80–89
Stage 2	140–159 or >160	90–99 or >100

Blood Disorders

• Anemia: Low RBCs or hemoglobin; decreased oxygen delivery.

• Sickle Cell Anemia: Abnormal hemoglobin; RBCs are sickle-shaped.

• Leukemia: Excess WBCs due to bone marrow cancer.

• Leukocytosis: High WBC count (infection or disease).

• Leukopenia: Low WBC count.

• Hemophilia: Inherited clotting disorder.

• Thrombocytopenia: Low platelet count.

• Polycythemia: Excess RBCs; thick blood, increased cardiac workload.

• Aneurysm: Localized vessel wall weakness; risk of rupture.

Immune System

White Blood Cells (WBCs) and Their Functions

• Neutrophils: Phagocytosis; first responders to bacterial infection.

• Eosinophils: Combat parasites; involved in allergic responses.

• Basophils: Release histamine and heparin; mediate inflammation and allergies.

• Monocytes: Phagocytosis; become macrophages in tissues, respond to chronic infection.

• Lymphocytes: Adaptive immunity; B-cells (antibody production), T-cells (attack infected/cancerous cells).

Lymphocytes: Types and Roles

• B-Cells: Produce antibodies (humoral immunity).

• T-Cells: Destroy infected or cancerous cells (cell-mediated immunity).

pH and Blood Homeostasis

• pH Scale: 0 (acidic) to 14 (basic); blood pH is 7.35–7.45.

• pH: Measures hydrogen ion concentration; critical for enzyme function and metabolic processes.

Respiratory System

Main Functions

• Gas exchange: Oxygen in, carbon dioxide out.

Respiration vs. Ventilation

• Respiration: Gas exchange at alveoli (external) and tissues (internal).

• Ventilation: Bulk movement of air in and out of lungs.

Respiratory Tract Anatomy

• Air Flow: Nose → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli

• Nose/Nasal Cavity: Filters, warms, moistens air.

• Pharynx: Passage for air and food; nasopharynx, oropharynx, laryngopharynx.

• Larynx: Contains vocal cords; routes air, prevents food entry.

• Trachea: Conducts air; reinforced with cartilage rings.

• Bronchi/Bronchioles: Branching airways; bronchioles lack cartilage.

• Alveoli: Gas exchange; surrounded by capillaries.

Alveolar Cells and Surfactant

• Type I (Squamous Pneumocytes): Thin, for gas exchange.

• Type II (Granular Pneumocytes): Produce surfactant (reduces surface tension, prevents collapse).

• Type III (Wandering Macrophages): Clean debris, move via pores of Kohn.

Lung Structure and Pleura

• Parietal Pleura: Lines thoracic cavity.

• Pleural Cavity: Fluid-filled space between pleurae.

• Visceral Pleura: Covers lung surface.

• Lobes: Right lung (3), left lung (2).

Control of Breathing

• Pontine Respiratory Center (Pons): Smooths breathing rhythm.

• Medullary Respiratory Center: Sets basic rhythm.

• Phrenic Nerve: Diaphragm control.

• Intercostal Nerves: Intercostal muscle control.

• Chemoreceptors: Central (medulla, CO2/pH), Peripheral (carotid/aortic bodies, O2/pH).

• Voluntary Control: Cerebral cortex (overridden by brainstem if CO2 rises).

Lung Volumes and Capacities

Term	Definition	Typical Value
Tidal Volume (TV)	Normal breath in/out	500 mL
Inspiratory Reserve Volume (IRV)	Max inhaled beyond normal	~3000 mL
Expiratory Reserve Volume (ERV)	Max exhaled beyond normal	~1200 mL
Residual Volume (RV)	Air left after max exhale	~1200 mL
Vital Capacity (VC)	Max air in/out in one cycle	~4800 mL
Total Lung Capacity (TLC)	All lung volumes combined	~6000 mL
Functional Residual Capacity (FRC)	Air left after normal exhale	~2400 mL

Respiratory Diseases

• Empyema: Pus in pleural cavity.

• Pneumothorax: Air in pleural space, lung collapse.

• Hemothorax: Blood in pleural space.

• Hemopneumothorax: Blood and air in pleural space.

• Atelectasis: Partial/total lung collapse (alveoli).

• Emphysema: Irreversible alveolar destruction, loss of elasticity.

• Lung Cancer: Malignant growth, often with hemoptysis (bloody sputum).

• Pneumonia: Infection/inflammation of lung tissue, fluid and debris accumulation.

Additional info:

• Some explanations (e.g., for diseases, hormone mechanisms, and blood cell production) have been expanded for clarity and completeness.

• Tables for hypertension stages and lung volumes have been recreated for study purposes.