Anatomy & Physiology: Essential Concepts

Anterior Pituitary Gland

The anterior pituitary gland is a major endocrine organ responsible for the secretion of several hormones that regulate various physiological processes.

• Location: Situated at the base of the brain, attached to the hypothalamus via the pituitary stalk.

• Hormones Released: Growth hormone (GH), prolactin (PRL), adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH), luteinizing hormone (LH).

• Functions:

  • GH: Stimulates growth and cell reproduction.

  • PRL: Promotes milk production.

  • ACTH: Stimulates cortisol release from adrenal cortex.

  • TSH: Stimulates thyroid hormone production.

  • FSH & LH: Regulate reproductive processes.

Parathyroid Gland

The parathyroid glands are small endocrine glands located on the posterior aspect of the thyroid gland, crucial for calcium homeostasis.

• Location: Usually four glands, embedded in the posterior surface of the thyroid.

• Hormone Produced: Parathyroid hormone (PTH).

• Function: PTH increases blood calcium levels by stimulating osteoclasts, increasing intestinal absorption, and promoting renal reabsorption of calcium.

• Cells Involved: Chief cells produce PTH.

Rh Factor and Pregnancy

The Rh factor is an antigen present on red blood cells. Its significance in pregnancy relates to Rh incompatibility between mother and fetus.

• Significance: Rh-negative mothers carrying Rh-positive fetuses may develop antibodies against fetal RBCs, risking hemolytic disease of the newborn.

• RhoGAM: An Rh immunoglobulin administered to Rh-negative women to prevent antibody formation.

Gradual Decrease of Steroid Prescription

Gradually tapering steroid medications is important to prevent adrenal insufficiency.

• Reason: Sudden cessation can suppress endogenous cortisol production, leading to withdrawal symptoms.

Blood Pressure Regulation

Blood pressure is regulated by various substances and mechanisms.

• Substances Increasing Blood Pressure: Epinephrine, norepinephrine, angiotensin II, aldosterone.

• Substances Decreasing Blood Pressure: Nitric oxide, atrial natriuretic peptide (ANP), prostaglandins.

Stroke Volume Equation

Stroke volume is the amount of blood ejected by the left ventricle per beat.

• Equation:

• Components:

  • End Diastolic Volume (EDV): Volume of blood in ventricle at end of filling.

  • End Systolic Volume (ESV): Volume of blood remaining after contraction.

Sickle Cell Disease

Sickle cell disease is a genetic disorder affecting hemoglobin structure.

• Treatment: Pain management, hydroxyurea, blood transfusions.

• Importance: Pain management is essential due to vaso-occlusive crises.

Hemostasis

Hemostasis is the process of stopping bleeding.

• Mechanisms: Vascular spasm, platelet plug formation, coagulation cascade.

• Cascade: Series of enzymatic reactions leading to fibrin clot formation.

Syncytium in Cardiac Muscle

A syncytium is a network of cells that function as a unit due to intercellular connections.

• Function: Allows coordinated contraction of cardiac muscle via gap junctions.

Intercalated Discs in Cardiac Muscle

Intercalated discs are specialized connections between cardiac muscle cells.

• Importance: Facilitate rapid transmission of electrical impulses and mechanical strength.

Plasma Proteins

Plasma proteins are essential for maintaining osmotic pressure, transport, and immunity.

• Examples and Functions:

  • Albumin: Maintains osmotic pressure.

  • Globulins: Immune function and transport.

  • Fibrinogen: Blood clotting.

Red Blood Cells (RBCs)

Red blood cells have a biconcave shape that enhances their function.

• Shape and Function: Biconcave shape increases surface area for gas exchange and flexibility.

• Nucleus: Mature RBCs lack a nucleus, allowing more room for hemoglobin.

• Intrinsic Factors: Vitamin B12 absorption is necessary for RBC production.

• Role in RBC Production: Intrinsic factor, produced in the stomach, enables B12 absorption in the ileum.

White Blood Cells (WBCs)

White blood cells are key components of the immune system.

• Types: Neutrophils, lymphocytes, monocytes, eosinophils, basophils.

• Functions:

  • Neutrophils: Phagocytosis of bacteria.

  • Lymphocytes: Adaptive immunity.

  • Monocytes: Differentiate into macrophages.

  • Eosinophils: Combat parasites.

  • Basophils: Release histamine.

Blood Pressure

Blood pressure is the force exerted by circulating blood on vessel walls.

• Normal Range: Systolic 90-120 mmHg, Diastolic 60-80 mmHg.

• Factors Increasing BP: Increased cardiac output, vasoconstriction, high sodium intake, stress.

• Hypertension Treatment: Antihypertensive medications such as ACE inhibitors, beta-blockers.

Heart Anatomy and Blood Flow

The heart is a muscular organ that pumps blood throughout the body.

• Labeling: Chambers (atria, ventricles), valves (tricuspid, mitral, pulmonary, aortic).

• Blood Flow Path: Blood returns from the femoral vein to the inferior vena cava, enters the right atrium, passes through the right ventricle, is pumped to the lungs via the pulmonary artery, returns to the left atrium via pulmonary veins, enters the left ventricle, and is pumped to the body via the aorta.