Study Guide: Endocrine, Cardiovascular, and Lymphatic Systems

Endocrine System

General Actions of Hormones

Hormones are chemical messengers secreted by endocrine glands into the bloodstream, where they regulate physiological processes throughout the body.

• Regulation: Hormones control growth, metabolism, reproduction, and homeostasis.

• Target Specificity: Each hormone affects only specific target cells with appropriate receptors.

• Feedback Mechanisms: Most hormone secretion is regulated by negative feedback loops.

• Example: Insulin lowers blood glucose, while glucagon raises it.

Peptide vs. Steroid Hormones

• Peptide Hormones: Made of amino acids; water-soluble; bind to plasma membrane receptors (e.g., insulin, growth hormone).

• Steroid Hormones: Derived from cholesterol; lipid-soluble; cross cell membranes and bind to intracellular receptors (e.g., cortisol, estrogen).

• Example: Insulin (peptide) acts quickly; cortisol (steroid) has longer-lasting effects.

Endocrine Control

• Endocrine Glands: Ductless glands that release hormones directly into the blood.

• Control Mechanisms: Include humoral (blood-borne signals), neural, and hormonal stimuli.

• Example: The hypothalamus controls the pituitary gland via releasing hormones.

Hormone Release Sites

• Pituitary Gland: Growth hormone, ACTH, TSH, etc.

• Thyroid Gland: Thyroxine (T4), triiodothyronine (T3)

• Adrenal Glands: Cortisol, aldosterone, epinephrine

• Pancreas (Islets of Langerhans): Insulin (beta cells), glucagon (alpha cells)

Beta Cell Products of the Pancreas

• Insulin: Lowers blood glucose by promoting cellular uptake of glucose.

• Amylin: Co-secreted with insulin; helps regulate glucose levels.

Blood Glucose and Insulin Variation

• High Blood Glucose: Stimulates insulin release; cells absorb glucose; blood sugar decreases.

• Low Blood Glucose: Inhibits insulin, stimulates glucagon; liver releases glucose.

Hormones Binding to Plasma Membranes

• Peptide Hormones: Bind to receptors on the cell surface; trigger second messenger systems (e.g., cAMP).

• Steroid Hormones: Typically do not bind to plasma membrane receptors.

Cardiovascular System: Blood

Whole Blood and Its Composition

• Whole Blood: A connective tissue consisting of plasma and formed elements.

• Plasma: Liquid matrix (~55% of blood); contains water, proteins (albumin, globulins, fibrinogen), nutrients, hormones, and waste products.

• Formed Elements: Cells and cell fragments (erythrocytes/RBCs, leukocytes/WBCs, platelets/thrombocytes).

Production of Blood Cells

• Hematopoiesis: Formation of blood cells in red bone marrow.

• Hematopoietic Stem Cells: Differentiate into all blood cell types.

Hematocrit

• Definition: Percentage of blood volume occupied by red blood cells.

• Normal Range: ~45% in males, ~42% in females.

Anemia

• Definition: A condition with reduced oxygen-carrying capacity of blood, often due to low RBC count or hemoglobin.

RBC Maturation and Hemoglobin Recycling

• Major Steps: Proerythroblast → Erythroblast → Reticulocyte → Erythrocyte (RBC)

• Hemoglobin Recycling: Heme is converted to biliverdin, then bilirubin; globin is broken down to amino acids.

• High Plasma Bilirubin: Causes jaundice (yellowing of skin/eyes).

Hemoglobin Structure

• Composition: 4 globin chains, each with a heme group containing iron.

Blood Types and Antigens

• Blood Types: Determined by presence of antigens (agglutinogens) on RBC membranes (A, B, AB, O).

• Antibodies: Present in plasma; react with foreign antigens.

RBC Lifespan

• Average Lifespan: ~120 days.

WBC Function

• Leukocytes: Defend against pathogens, remove toxins and debris.

Platelets/Thrombocytes

• Definition: Cell fragments involved in blood clotting.

Vascular Spasm and Fibrinolysis

• Vascular Spasm: Immediate constriction of a damaged blood vessel; reduces blood loss.

• Fibrinolysis: Breakdown and removal of a blood clot after healing.

Cardiovascular System: Heart

Heart Structures and Functions

• Valves: Ensure one-way blood flow (tricuspid, bicuspid/mitral, pulmonary, aortic).

• Chordae Tendineae: Prevent valve prolapse during ventricular contraction.

Heart Layers and Membranes

• Epicardium: Outer layer (visceral pericardium).

• Myocardium: Muscular middle layer.

• Endocardium: Inner lining of heart chambers.

Blood Flow Through the Heart

• Right atrium → tricuspid valve → right ventricle → pulmonary valve → pulmonary artery → lungs → pulmonary veins → left atrium → bicuspid/mitral valve → left ventricle → aortic valve → aorta → body

Electrical Events: P, QRS, and T Waves

• P Wave: Atrial depolarization

• QRS Complex: Ventricular depolarization

• T Wave: Ventricular repolarization

Systole and Diastole

• Systole: Contraction phase (blood ejected from chambers)

• Diastole: Relaxation phase (chambers fill with blood)

Heart Sounds

• Causes: Closing of heart valves ("lub-dub")

Stroke Volume (SV), Cardiac Output (CO), and Heart Rate (HR)

• Stroke Volume (SV): Volume of blood pumped by one ventricle per beat.

• Cardiac Output (CO): Volume of blood pumped by each ventricle per minute.

• Heart Rate (HR): Number of heart beats per minute.

• Formulas:

$CO = SV \times HR$

Cardiovascular System: Blood Vessels

Blood Vessel Structure and Function

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

• Veins: Carry blood toward the heart; thinner walls, valves present.

• Capillaries: Site of exchange between blood and tissues; thin walls.

Blood Pressure

• Definition: Force exerted by blood on vessel walls.

• Systolic Pressure: During ventricular contraction.

• Diastolic Pressure: During ventricular relaxation.

Water and Solute Reabsorption

• Capillary Exchange: Water and solutes move between blood and tissues via filtration and reabsorption.

Arterial and Venous Supply/Drainage

• Arteries: Supply oxygenated blood to tissues.

• Veins: Drain deoxygenated blood from tissues.

Lymphatic System

Parallels with Cardiovascular System

• Both: Consist of vessels that transport fluid throughout the body.

• Lymphatic Vessels: Return excess interstitial fluid to the bloodstream.

Pathways of Lymph Fluid

• Lymph capillaries → lymph vessels → lymph nodes → lymph trunks → lymph ducts → subclavian veins

Lymph Node Concentration

• Major Areas: Cervical, axillary, and inguinal regions.

Examples of MALT (Mucosa-Associated Lymphoid Tissue)

• Tonsils, Peyer's patches (in small intestine), appendix

Location and Properties of Lymphatic Organs

• Primary Organs: Red bone marrow, thymus (site of lymphocyte production/maturation)

• Secondary Organs: Lymph nodes, spleen, MALT (site of immune responses)

Blood Component	Main Function	Key Properties
Red Blood Cells (Erythrocytes)	Transport oxygen and carbon dioxide	Biconcave, no nucleus, contain hemoglobin
White Blood Cells (Leukocytes)	Immune defense	Various types (neutrophils, lymphocytes, etc.)
Platelets (Thrombocytes)	Blood clotting	Cell fragments, initiate clotting cascade
Plasma	Transport medium	Water, proteins, nutrients, hormones

Additional info: Some explanations and examples were expanded for clarity and completeness based on standard anatomy and physiology textbooks.