Question

MCAT Tutorial: The Circulatory System

Answer 1

pulmonary: circulation of blood through the lungs
systemic: circulation of blood through the other parts of the body

\({\bf{Structure~of~the~Heart:}}\)

note: "right" and "left" are the opposite since it's taken from the perspective of the person the heart is inside

- atria: two upper chambers
- ventricles: two lower chambers
- septum: separates left and right sides of the heart
- valves: four valves, one between each two chambers, keep blood flowing in one direction
> atrioventicular valves: separate atria and ventricles
- tricuspid: right side valve, mitral: left side valve
> semilunar valves: prevent blood from re-entering the ventricles
- pulmonary valve: right ventricle; aortic valve: left ventricle

general path: deoxygenated blood --> right atrium --> right ventricle --> pulmonary arteries --> lungs --> pulmonary veins --> left atrium --> left ventricle --> body --> deoxygenated blood --> repeat cycle

Answer 2

\({\bf{Arterial~and~Venous~Systems:}}\)
- arteries: blood vessels that carry blood away from heart, strong, smooth muscle
- aorta: largest artery
- arterioles: branch of arteries leading into the capillaries
- veins: carry blood to the heart; less elastic, no smooth muscle, require skeletal system assistance
- venules: small veins that collect blood from capillaries
- capillaries: narrow blood vessels between arterioles and venules, site of nutrient/waste exchange

general path: aorta --> capillaries --> veins --> heart (superior and inferior vena cava)

\({\bf{Blood~Pressure:}}\)
- systolic pressure: maximum pressure exerted on the blood vessel walls (contraction)
- diastolic: minimm
- blood pressure: measurement of blood pressure, systolic/diastolic, mmHg
- Starling forces: change the blood pressure depending on the blood vessel type
- capillaries: osmotic pressure caused by solute gradient --> fluids move from tissues into capillaries

\({\bf{Blood~Composition:}}\)
- blood plasma: water + ions + hormones + glucose, CO2, blood proteins
- blood cells:
> erythrocytes: red blood cells, transport oxygen, anaerobic
> leukocytes: immune cells
> platelets: form clots, normally inactivated by endothelial cells until injury
- coagulation: process by which platelets bind collagen and create a platelet plug

\({\bf{Oxygen~Transport:}}\)
- most oxygen is cooperatively bound by hemoglobin
- hematocrit: proportion of blood composed of erythrocytes (about 48% in men, 38% in women)
- in order of least to highest density: plasma, leukocytes, platelets, erythrocytes

\({\bf{Homeostatis:}}\)
- thermoregulation: regulation of body temperature
- vasodilation: expansion of arterioles and increase of blood flow through arteries/capillaries/veins, cooling effect
- vasoconstriction: contraction of blood vessels, warming effect
- osmolality: concentration of solutes in blood
> regulated by fluid release/reabsorption in capillaries
> ADH/aldosterone: increase blood volume and water reabsorption

Answer 3

Anyway, that's the end of my tutorial, I hope it was a helpful resource. Source material is the 2nd Edition Barron's Prep book for the new MCAT