A&P Study Guide: The Endocrine System, Blood, and The Heart

Chapter 16: The Endocrine System

Overview of the Endocrine System

The endocrine system is a network of glands that secrete hormones directly into the bloodstream to regulate various body functions. Hormones act as chemical messengers, influencing growth, metabolism, reproduction, and homeostasis.

• Hormones: Chemical messengers released into the blood to regulate target cell activity.

• Endocrinology: The scientific study of hormones and endocrine glands.

• Target Cells: Cells with specific receptors for a given hormone.

Major Functions of Hormones

• Regulate growth and development

• Control metabolism and energy balance

• Direct reproductive processes

• Mediate stress responses

• Maintain fluid and electrolyte balance

• Regulate blood pressure and blood glucose

• Preserve homeostasis

Exocrine vs. Endocrine Glands

Exocrine Glands	Endocrine Glands
Have ducts	Ductless
Secrete onto body surfaces	Secrete into blood
Example: Sweat glands	Example: Thyroid gland

Stimuli for Hormone Release

• Humoral: Changes in blood levels of ions/nutrients (e.g., low Ca2+ triggers PTH release).

• Neural: Nerve fibers stimulate hormone release (e.g., sympathetic stimulation of adrenal medulla).

• Hormonal: Hormones stimulate other glands to release hormones (e.g., TSH stimulates thyroid hormones).

Hormone Interactions

• Permissiveness: One hormone enables another to act.

• Synergism: Combined effect is greater than individual effects.

• Antagonism: Hormones oppose each other's actions (e.g., insulin vs. glucagon).

Major Endocrine Glands and Hormones

Gland	Hormone(s)	Main Function(s)
Pituitary (Anterior)	GH, TSH, ACTH, FSH, LH, PRL	Growth, thyroid/adrenal stimulation, reproduction, milk production
Pituitary (Posterior)	ADH, Oxytocin	Water retention, labor, milk ejection
Thyroid	T3, T4, Calcitonin	Metabolism, growth, lowers blood calcium
Parathyroid	PTH	Raises blood calcium
Adrenal Cortex	Aldosterone, Cortisol, Androgens	Sodium retention, stress response, sex hormone precursors
Adrenal Medulla	Epinephrine, Norepinephrine	Fight-or-flight response
Pineal	Melatonin	Sleep-wake cycle
Pancreas	Insulin, Glucagon	Blood glucose regulation

Examples:

• Insulin: Lowers blood glucose by promoting cellular uptake.

• Glucagon: Raises blood glucose by stimulating glycogen breakdown.

• PTH: Increases blood calcium by stimulating bone resorption.

• Calcitonin: Lowers blood calcium by inhibiting bone resorption.

Chapter 17: Blood

Composition and Functions of Blood

Blood is a specialized connective tissue composed of plasma and formed elements. It transports substances, regulates body conditions, and protects against disease.

• Plasma: Liquid matrix (90% water) containing proteins, nutrients, hormones, and electrolytes.

• Formed Elements: Erythrocytes (RBCs), leukocytes (WBCs), and platelets.

Functions of Blood

• Transport of gases (O2, CO2), nutrients, wastes, and hormones

• Temperature and pH regulation

• Clotting to prevent blood loss

• Immune defense against pathogens

Plasma Proteins

• Albumin: Most abundant; maintains osmotic pressure and transports substances.

Erythrocytes (Red Blood Cells)

• Biconcave, anucleate, 7.5 μm diameter

• Transport O2 (via hemoglobin) and CO2

• No mitochondria; rely on anaerobic metabolism

Hemoglobin Structure

• 4 globin chains + 4 heme groups (each with 1 iron atom)

• Each hemoglobin binds up to 4 O2 molecules

Hematopoiesis and Erythropoiesis

• Hematopoiesis: Formation of blood cells in red bone marrow

• Erythropoiesis: RBC production, stimulated by erythropoietin (EPO) from kidneys in response to hypoxia

Blood Disorders

• Anemia: Reduced oxygen-carrying capacity (due to blood loss, low RBC production, or increased destruction)

• Polycythemia: Excess RBCs, causing thick blood and increased clot risk

• Sickle Cell Anemia: Abnormal hemoglobin (HbS) causes sickled RBCs and vessel blockage

• Thalassemias: Reduced globin production, leading to anemia

Leukocytes (White Blood Cells)

• Granulocytes: Neutrophils (bacteria), Eosinophils (parasites/allergies), Basophils (histamine/heparin)

• Agranulocytes: Lymphocytes (immunity), Monocytes (macrophages)

• Leukocytosis: Elevated WBC count, usually due to infection

• Leukemia: Cancer of blood-forming tissues; excess abnormal WBCs, anemia, bleeding, infection

Platelets and Hemostasis

• Platelets: Cell fragments from megakaryocytes; essential for clotting

1. Vascular Spasm: Vessel constriction

2. Platelet Plug Formation: Platelets adhere to injury site

3. Coagulation: Fibrin clot forms

4. Clot Retraction: Clot shrinks

5. Fibrinolysis: Clot dissolves

Blood Typing

Blood Type	Antigen(s)	Antibody(ies)
A	A	Anti-B
B	B	Anti-A
AB	A and B	None
O	None	Anti-A & Anti-B

• Rh Factor: D antigen present (Rh+) or absent (Rh-)

Common Blood Tests

Test	Evaluates
CBC (Complete Blood Count)	RBCs, WBCs, hemoglobin, hematocrit, platelets
CMP (Comprehensive Metabolic Panel)	Glucose, electrolytes, kidney/liver function, proteins, acid-base balance

Chapter 18: The Cardiovascular System — The Heart

Functions of the Heart

The heart is a muscular organ that pumps blood through the pulmonary and systemic circuits, delivering oxygen and nutrients, removing wastes, and maintaining blood pressure.

• Pumps blood through pulmonary (lungs) and systemic (body) circuits

• Delivers oxygen and nutrients

• Removes metabolic wastes

• Maintains blood pressure

Pulmonary vs. Systemic Circuits

Pulmonary Circuit	Systemic Circuit
Right heart → lungs → left heart	Left heart → body tissues → right heart
Oxygenates blood	Delivers oxygen, removes CO2

Blood Flow Pathway

1. Body → Superior/Inferior Vena Cava

2. Right Atrium → Tricuspid Valve → Right Ventricle

3. Pulmonary Semilunar Valve → Pulmonary Trunk → Pulmonary Arteries → Lungs

4. Pulmonary Veins → Left Atrium → Mitral Valve → Left Ventricle

5. Aortic Semilunar Valve → Aorta → Body

Heart Anatomy

• Size: About the size of a closed fist (250–350 g)

• Location: Mediastinum (thoracic cavity, between lungs)

• Orientation: Base (superior, formed by atria); Apex (inferior, formed by left ventricle, points left)

Heart Wall Layers

• Pericardium: Protective sac (fibrous and serous layers)

• Epicardium: Outer layer (visceral serous pericardium)

• Myocardium: Cardiac muscle tissue (thickest in left ventricle)

• Endocardium: Inner lining (simple squamous epithelium)

Chambers of the Heart

• Atria (superior): Receive blood (right: venae cavae & coronary sinus; left: pulmonary veins)

• Ventricles (inferior): Pump blood out (right: to lungs; left: to body)

• Interatrial Septum: Separates atria; contains fossa ovalis

• Interventricular Septum: Separates ventricles; contains conduction fibers

External Landmarks

• Coronary Sulcus: Encircles heart, separates atria and ventricles, contains coronary vessels

• Anterior/Posterior Interventricular Sulci: Mark ventricular separation, contain major arteries

Heart Valves

• Atrioventricular (AV) Valves: Between atria and ventricles (right: tricuspid; left: mitral/bicuspid)

• Supported by chordae tendineae and papillary muscles

• Semilunar (SL) Valves: Between ventricles and arteries (pulmonary and aortic); prevent backflow

Coronary Circulation

• Coronary Arteries: Supply myocardium (RCA and LCA with branches)

• Coronary Sinus: Main venous drainage into right atrium

• Major Veins: Great, middle, and small cardiac veins

Homeostatic Imbalances

• Angina Pectoris: Temporary myocardial ischemia; chest pain without permanent damage

• Myocardial Infarction (MI): Heart attack; complete coronary blockage, cardiac muscle death, permanent damage

Microscopic Anatomy of Cardiac Muscle

• Endomysium: Connective tissue around muscle fibers

• Intercalated Discs: Specialized junctions for coordinated contraction

• Desmosomes: Mechanical junctions preventing cell separation

• Gap Junctions: Allow ion flow for rapid action potential spread

• Cardiac Muscle: Striated, branched, usually one nucleus, involuntary

Intrinsic Conduction System

• Generates and conducts electrical impulses independently of nervous system

• SA Node (Pacemaker): Initiates impulses, sets heart rate (60–100 bpm)

• Sequence: SA Node → AV Node (delay) → AV Bundle (Bundle of His) → Bundle Branches → Purkinje Fibers → Ventricular contraction

Mnemonic:

• SABBP: SA Node, AV Node, Bundle of His, Bundle Branches, Purkinje Fibers

High-Yield Exam Memorization List

• Draw and trace the heart blood-flow pathway

• Trace the cardiac conduction pathway

• Identify all major endocrine hormones and functions

• Explain hematopoiesis and blood typing

Key Facts:

• Insulin: Moves glucose into cells

• Glucagon: Raises blood glucose

• PTH: Raises blood calcium

• Calcitonin: Lowers blood calcium

• ADH: Promotes water reabsorption

• RBC: Oxygen transport

• WBC: Defense

• Platelets: Clotting

• Albumin: Maintains osmotic pressure

• EPO: Stimulates RBC production

• Angina: Temporary ischemia

• MI: Permanent cardiac muscle death

Additional info:

• For equations related to blood pressure, cardiac output, or hormone feedback, refer to the following:

Cardiac Output Equation:

$CO = HR \times SV$

Where $CO$ is cardiac output, $HR$ is heart rate, and $SV$ is stroke volume.

Mean Arterial Pressure (MAP):

$MAP = CO \times TPR$

Where $TPR$ is total peripheral resistance.