Exam 4: Endocrine, Circulatory, and Respiratory Systems

What do endocrine glands secrete?

Hormones, which are chemical messengers in the bloodstream.

How do hormones affect target cells?

Hormones exert specific effects on target cells throughout the body.

What are target cells?

Cells that have receptors for specific hormones.

What is the function of the endocrine system?

To communicate and regulate bodily activities through the release of hormones.

Where is the pituitary gland located?

Inferior to the hypothalamus, sitting in the sella turcica of the sphenoid bone.

How is the pituitary gland connected to the hypothalamus?

By the infundibulum.

What is the hypothalamic-pituitary axis?

The communication pathway between the hypothalamus and the pituitary gland.

What are the two lobes of the pituitary gland?

The anterior pituitary (epithelial tissue) and the posterior pituitary (nervous tissue).

How does the hypothalamus communicate with the anterior pituitary?

Via the hypophyseal portal system, which is a double capillary bed.

What type of hormones does the hypothalamus secrete to control the anterior pituitary?

Releasing or inhibiting hormones.

What are some examples of hypothalamic hormones that control the anterior pituitary?

GnRh, CRH, TRH, PRH, and GHRH.

What is the role of the posterior pituitary?

To store hormones produced in the hypothalamus and release them in response to neural signals.

Where are the adrenal glands located?

Superior to the kidneys.

What are the two main parts of the adrenal gland?

The adrenal cortex and the adrenal medulla.

What type of hormones does the adrenal cortex secrete?

Steroid hormones.

What is cortisol and its function?

A glucocorticoid that helps the body respond to stress by increasing energy availability, repairing tissues, and immunosuppression.

What is aldosterone and its role?

A mineralocorticoid that conserves fluid and increases blood pressure.

What hormones are secreted by the adrenal medulla?

Epinephrine and norepinephrine.

What is the function of epinephrine and norepinephrine?

To act like widespread sympathetic nervous system stimulation.

Where is the pancreas located?

Posterior and inferior to the stomach.

What are the types of cells found in pancreatic islets?

Beta (β) cells that secrete insulin and Alpha (α) cells that secrete glucagon.

What is the function of insulin?

Insulin lowers blood sugar levels.

What is the function of glucagon?

Glucagon raises blood sugar levels.

What are the main components of blood?

Blood consists of plasma and formed elements.

What percentage of blood volume does plasma make up?

Approximately 55%.

What does plasma contain?

Ions, nutrients, hormones, gases, and proteins such as albumin, globulins, and fibrinogen.

What are formed elements in blood?

Less than 1% as the buffy coat (leukocytes and platelets) and about 45% as hematocrits (erythrocytes).

What is the diameter of capillaries compared to erythrocytes?

Capillaries have a diameter of 8-10 µm, slightly larger than erythrocytes at 7.5 µm.

What is the primary function of erythrocytes?

Erythrocytes, or red blood cells (RBCs), are primarily responsible for oxygen transport.

What shape do mature erythrocytes have and why?

They have a biconcave shape to provide more surface area for faster diffusion of gases.

What is hemoglobin and its role in erythrocytes?

Hemoglobin (Hb) is an iron-containing gas-transport protein that makes up about 97% of RBC content and binds oxygen.

What stimulates erythropoiesis?

Erythropoiesis is stimulated by the hormone erythropoietin (EPO).

Where is erythropoietin primarily produced?

EPO is primarily produced by the kidneys in response to low blood oxygen levels.

What is the lifespan of red blood cells?

RBCs have a limited lifespan of about 120 days.

What is anemia?

Anemia is a condition characterized by insufficient RBCs or hemoglobin, resulting in low blood oxygen carrying capacity.

What are the two main circuits of blood circulation?

Pulmonary circulation and systemic circulation.

What happens in pulmonary circulation?

The right side of the heart receives oxygen-poor blood from the body and pumps it to the lungs.

What happens in systemic circulation?

The left side of the heart receives oxygen-rich blood from the lungs and pumps it throughout the body.

What are the layers of the heart wall?

The heart wall has three layers: epicardium, myocardium, and endocardium.

What is the function of the fibrous pericardium?

The fibrous pericardium protects the heart and anchors it.

What is the serous pericardium?

The serous pericardium is a double-walled layer deep to the fibrous pericardium.

What are the two layers of the serous pericardium?

The parietal layer, which lines the internal surface of the fibrous pericardium, and the visceral layer (epicardium), which lies directly on the surface of the heart.

What is the function of serous fluid in the pericardial cavity?

Serous fluid reduces friction as the heart beats.

What is the pericardial cavity?

The space between the parietal and visceral layers of the serous pericardium, containing serous fluid.

What are the four chambers of the heart?

The right atrium, right ventricle, left atrium, and left ventricle.

What is the primary function of the atria?

The atria primarily receive blood, and their pumping is aided by gravity.

Why do ventricles have thicker walls than atria?

Ventricles pump blood against gravity with more force.

What is the coronary (atrioventricular) sulcus?

A groove that divides the atria and ventricles.

What is the function of the apex of the heart?

The apex is the inferior tip of the heart.

What is the base of the heart?

The posterior surface of the heart, opposite the apex.

What are septa in the heart?

Walls that separate the heart chambers; the interatrial septum separates the atria, and the interventricular septum separates the ventricles.

What are the two types of valves in the heart?

Atrioventricular (AV) valves and semilunar valves.

What are the names of the AV valves?

The right AV valve (tricuspid) and the left AV valve (bicuspid or mitral).

What heart sound is produced by the closing of the AV valves?

The first heart sound, known as 'lub'.

What are the semilunar valves?

Valves located between the ventricles and the great arteries; the pulmonary semilunar valve is between the right ventricle and pulmonary trunk, and the aortic semilunar valve is between the left ventricle and aorta.

What heart sound is produced by the closing of the semilunar valves?

The second heart sound, known as 'dub'.

What are papillary muscles?

Cone-shaped muscles in the ventricles.

What is the function of chordae tendineae?

Fibrous strings that attach AV valve cusps to papillary muscles, preventing prolapse into the atria.

What is the fibrous skeleton (cardiac skeleton) of the heart?

Dense connective tissue around all four valves, anchoring cusps and blocking direct spread of electrical impulses.

What are the venous openings in the heart?

The superior and inferior vena cava (right atrium), pulmonary veins (left atrium), and coronary sinus (right atrium).

What are the arterial openings in the heart?

The pulmonary trunk (right ventricle), aorta (left ventricle), and right and left coronary arteries (aorta).

What is the path of deoxygenated blood through the heart?

Deoxygenated blood enters the right atrium via the superior and inferior vena cava, passes through the right AV valve into the right ventricle, and is pumped through the pulmonary semilunar valve into the pulmonary trunk to the lungs.

What happens to oxygenated blood after it returns to the heart?

Oxygenated blood returns to the left atrium via the pulmonary veins, passes through the left AV valve into the left ventricle, and is pumped through the aortic semilunar valve into the aorta to the body.

What are septal wall defects?

Holes in the wall separating heart chambers that allow mixing of oxygenated and deoxygenated blood, reducing oxygen delivery to tissues.

What are the two main coronary arteries and where do they arise from?

The right and left coronary arteries arise from the aorta.

What are the branches of the left coronary artery?

The left coronary artery branches into the anterior interventricular (left anterior descending artery, LAD) and the circumflex artery (which branches into the left marginal artery).

What are the branches of the right coronary artery?

The right coronary artery branches into the right marginal artery and the posterior interventricular artery (posterior descending artery, PDA).

How do coronary veins function in the heart?

Coronary veins run alongside coronary arteries and drain into the coronary sinus on the posterior side, returning deoxygenated blood to the right atrium.

What is a myocardial infarction?

A myocardial infarction, or heart attack, is the death of cardiac muscle tissue due to lack of blood supply, typically caused by a blockage in a coronary artery.

What is the role of the sinoatrial (SA) node in the heart?

The SA node, located in the right atrium, generates electrical impulses that initiate the heartbeat.

What is the sequence of electrical impulse conduction in the heart?

1. SA node generates impulses. 2. Impulses spread through the atria, causing contraction. 3. Impulses reach the AV node, introducing a delay. 4. Impulse travels down the AV bundle (bundle of His). 5. AV bundle branches into right and left bundle branches. 6. Impulses carried by Purkinje fibers throughout the ventricles.

What is automaticity in cardiac muscle cells?

Automaticity (autorhythmicity) is the ability of some cardiac muscle cells to spontaneously depolarize.

What are systole and diastole in the cardiac cycle?

Systole is the contraction of the heart chamber, pumping blood out. Diastole is the relaxation (dilation) of a heart chamber as it fills with blood.

What causes the 'lub' heart sound?

The 'lub' heart sound is caused by the closing of the AV valves at the beginning of ventricular systole.

What causes the 'dub' heart sound?

The 'dub' heart sound is caused by the closing of the semilunar valves at the beginning of ventricular diastole.

Why do the atria and ventricles not contract simultaneously?

Atria and ventricles do not contract simultaneously due to the delay at the AV node.

What is the function of arteries?

Arteries carry blood away from the heart.

What is the function of capillaries?

Capillaries are small vessels where the exchange of substances with tissues occurs.

What is the function of veins?

Veins carry blood toward the heart and have lower blood pressure than arteries.

What are elastic arteries and give an example?

Elastic arteries are the largest arteries with high elastin content, such as the aorta.

What are muscular arteries and give an example?

Muscular arteries are distal to elastic arteries and have a thick tunica media, such as the brachial artery.

What are resistance arteries and arterioles?

Resistance arteries and arterioles are distal to muscular arteries and regulate blood flow and pressure.

What are venules?

Venules are small veins formed by the union of capillaries.

What are the three tunics of blood vessels?

1. Tunica Intima (inner layer): Simple squamous epithelium. 2. Tunica Media (middle layer): Smooth muscle and elastic fibers. 3. Tunica Externa (outer layer): Connective tissue.

What are continuous capillaries?

Continuous capillaries are the most common type, allowing movement of water and small molecules through intercellular clefts.

What are fenestrated capillaries and where are they found?

Fenestrated capillaries have pores (fenestrations) allowing passage of slightly larger molecules and are found in areas with high exchange rates, such as endocrine glands.

What are sinusoids?

Sinusoids are the widest and leakiest capillaries with large fenestrations and wide intercellular clefts.

What is the function of the blood-brain barrier?

It allows the passage of blood cells and large proteins, providing a selective permeability in the brain.

What is an anastomosis in the circulatory system?

It is a connection or joining of blood vessels that provides alternate routes for blood flow.

What is the common circulatory route for blood flow?

Arteriole -> capillary bed -> venule.

What are portal systems in the circulatory system?

They consist of two capillary beds connected by a vein.

What is the hypophyseal portal system?

It connects the hypothalamus to the anterior pituitary.

What is the hepatic portal system?

It connects abdominal organs (except kidneys) to the liver.

Describe pulmonary circulation.

It is the flow of blood from the right ventricle to the lungs and then to the left atrium, operating at low pressure.

Describe systemic circulation.

It is the flow of blood from the left ventricle to the body and then to the right atrium, operating at high pressure.

What regulates blood flow through capillary beds?

Vasomotion of precapillary sphincters.

What happens when precapillary sphincters are constricted?

Blood bypasses true capillaries and flows directly from the metarteriole to the thoroughfare channel.

What are the major arteries in the head and neck?

External and internal carotids, and the cerebral arterial circle.

What does the celiac trunk supply?

It supplies the stomach, spleen, and liver.

What is the function of the superior vena cava?

It returns blood from above the diaphragm.