Key Concepts in Human Physiology and Anatomy

Nephron

Functional unit of the kidney; filters blood, reabsorbs nutrients, and secretes wastes.

GFR (Glomerular Filtration Rate)

Rate at which filtrate is formed; normal is ~125 mL/min.

ADH (Antidiuretic Hormone)

Increases water reabsorption at DCT and collecting duct.

Aldosterone

Promotes sodium reabsorption in the DCT, increasing blood pressure.

Renin-Angiotensin-Aldosterone System (RAAS)

Hormonal system regulating blood pressure and fluid balance.

Filtration

Movement of water and solutes out of glomerular capillaries into the nephron.

Reabsorption

Movement of substances from filtrate back into the blood.

Secretion

Transfer of substances from blood into tubular fluid.

Urinalysis

Diagnostic test for evaluating urine composition (e.g., glucose, proteins, blood).

Micturition Reflex

Reflex triggering urination via bladder stretch receptors.

Alimentary Canal

Mouth to anus; includes esophagus, stomach, intestines.

Peristalsis

Involuntary waves of muscle contraction that move food.

Villi & Microvilli

Increase surface area in small intestine for absorption.

Chief Cells

Secrete pepsinogen in the stomach.

Parietal Cells

Secrete HCl and intrinsic factor.

Bile

Emulsifies fats; produced in liver, stored in gallbladder.

Amylase

Digests starch into sugars; found in saliva and pancreatic juice.

Pepsin

Protein-digesting enzyme activated by stomach acid.

Lipase

Breaks down lipids into fatty acids and glycerol.

Defecation Reflex

Triggered by rectal wall stretch, results in elimination of feces.

Pulmonary Ventilation

Breathing; movement of air into and out of lungs.

Alveoli

Site of gas exchange; surrounded by capillaries.

Dorsal Respiratory Group (DRG) and Ventral Respiratory Group (VRG)

Respiratory control centers in the medulla oblongata.

External Respiration

Gas exchange between alveoli and blood.

Internal Respiration

Gas exchange between blood and tissues.

Hypercapnia

Elevated CO₂ levels; triggers increased respiration.

Hypocapnia

Low CO₂; can result from hyperventilation.

Compliance

Measure of lung expandability.

Pneumothorax

Collapsed lung due to air in pleural cavity.

Partial Pressure

Pressure of individual gas in a mixture; drives diffusion.

Cardiac Output (CO)

Heart rate × stroke volume.

Preload

Stretch of ventricular walls before contraction.

Afterload

Resistance the heart must overcome to eject blood.

Baroreceptors

Detect changes in blood pressure.

Capillaries

Smallest vessels where exchange occurs.

Thoracic Duct

Returns lymph to left subclavian vein.

Lymph Node

Filters lymph; contains immune cells.

NK Cells

Natural killer cells; destroy infected cells non-specifically.

Complement System

Plasma proteins that aid immunity via classical or alternative pathways.

Inflammation

Nonspecific response to tissue injury; includes redness, heat, swelling, pain.

Insulin

Secreted by beta cells; lowers blood glucose.

Glucagon

Secreted by alpha cells; raises blood glucose.

Melatonin

Secreted by pineal gland; regulates circadian rhythms.

Type I Diabetes

Autoimmune destruction of beta cells.

Type II Diabetes

Insulin resistance; often linked to obesity.

ADH

Retains water; secreted by posterior pituitary.

Adrenocorticotropic hormone (ACTH)

Stimulates cortisol release from adrenal cortex.

Thyroid-stimulating hormone (TSH)

Stimulates thyroid gland to release T₃ and T₄.

Cortisol

Stress hormone; increases blood glucose.

Erythropoietin (EPO)

Stimulates red blood cell production.

Acidosis

Blood pH < 7.35.

Alkalosis

Blood pH > 7.45.

Respiratory Acidosis

Due to CO₂ retention (e.g., hypoventilation).

Metabolic Acidosis

Due to increased H⁺ (hydrogen ions) or loss of HCO₃⁻ (bicarbonate ions).

Buffer System

Maintains pH using weak acid/base pairs (e.g., bicarbonate).

Compensation

Respiratory or renal response to correct pH imbalance.

Bicarbonate (HCO₃⁻)

Key buffer in plasma.

Hypoventilation

Slows breathing; leads to CO₂ buildup.

Hyperventilation

Rapid breathing; causes CO₂ loss.

Diagnostic Values

pH, PCO₂, and HCO₃⁻ used to assess acid-base status.

Spermatogenesis

Sperm production in seminiferous tubules.

Oogenesis

Egg production in ovaries.

LH (Luteinizing Hormone)

Triggers ovulation and testosterone production.

FSH (Follicle-Stimulating Hormone)

Stimulates gamete production.

Testosterone

Male sex hormone from interstitial cells.

Estrogen

Female hormone that promotes secondary sex traits and endometrial growth.

Progesterone

Maintains endometrial lining post-ovulation.

Menstrual Phase

Shedding of endometrial lining.

Secretory Phase

Endometrium prepares for implantation.

Ovulation

Release of secondary oocyte from ovary.

Edema

Swelling caused by excess fluid trapped in the body’s tissues, often due to increased capillary filtration or decreased reabsorption.

Mitosis

produces 2 identical diploid cells.

Meiosis

produces 4 genetically unique haploid gametes.

ECG measure

Electrical activity of the heart, showing P wave (atrial depolarization), QRS complex (ventricular depolarization), and T wave (ventricular repolarization).

Contractility

The strength of the heart's contraction, independent of preload.

Cardiac action potential differ from skeletal muscle AP

has a plateau phase due to calcium influx, preventing tetanus.

Asthma

chronic condition causing airway inflammation and bronchoconstriction, leading to difficulty breathing.

Stroke

A sudden loss of brain function due to disrupted blood supply—either ischemic or hemorrhagic.

Aneurysm

A weakened, bulging section of a blood vessel that can rupture.

Chronic Obstructive Pulmonary Disease (COPD)

—includes emphysema and chronic bronchitis; causes airflow limitation.

Emphysema

A form of COPD characterized by alveolar wall destruction and reduced respiratory surface area.

Cirrhosis

Chronic liver damage from various causes leading to scarring and liver failure.

Deep vein thrombosis (DVT)

A blood clot in a deep vein, usually in the legs, which can lead to pulmonary embolism.

Hemorrhage

Excessive bleeding either externally or internally due to ruptured blood vessels.