Heart & Circulation

Formed elements of blood

Erythrocytes, leukocytes, platelets

Plasma

Liquid portion of blood containing water, proteins, nutrients, hormones

Where blood cells are made

Red bone marrow

Blood stem cell

Hemocytoblast (hematopoietic stem cell)

Hemoglobin

Oxygen‑carrying protein in RBCs

Anemia

Low oxygen‑carrying capacity of blood

Why anemia causes problems

Tissues receive insufficient oxygen

White blood cell types

Neutrophils, eosinophils, basophils, lymphocytes, monocytes

Neutrophil function

Phagocytosis of bacteria

Eosinophil function

Fight parasites; involved in allergies

Basophil function

Release histamine and heparin

Lymphocyte function

Adaptive immunity (B cells, T cells, NK cells)

Monocyte function

Become macrophages; phagocytosis

Fibrinolysis

Breakdown of a blood clot

Most abundant plasma protein

Albumin

Other plasma proteins and functions

Globulins (antibodies), fibrinogen (clotting)

Hormone stimulating RBC formation

Erythropoietin (EPO)

Where EPO is released

Kidneys

How CO2 is carried in blood

Mostly as bicarbonate; some bound to hemoglobin; some dissolved

How O2 is carried in blood

Bound to hemoglobin

Vitamin important for clotting

Vitamin K

Heart covering

Pericardium

Divisions of pericardium

Fibrous pericardium and serous pericardium

Outermost pericardial layer

Fibrous pericardium

Innermost pericardial layer

Visceral pericardium (epicardium)

What is between pericardial layers

Serous fluid

Epicardium vs visceral pericardium

Same structure

Four chambers of the heart

Right atrium, right ventricle, left atrium, left ventricle

Four valves of the heart

Tricuspid, pulmonary, mitral, aortic

Chordae tendineae

Tendinous cords preventing valve prolapse

Papillary muscles

Muscles that pull chordae tendineae during contraction

Why left ventricle is thicker

Pumps blood to entire body (higher pressure)

Auricle

Flap-like extension of atria that increases volume

Three circulatory routes

Systemic, pulmonary, coronary

Start of systemic circulation

IVC/SVC → right atrium

Importance of coronary circulation

Supplies oxygen to heart muscle

Vessels in coronary circulation

Coronary arteries, cardiac veins, coronary sinus

Where heartbeat starts

SA node

Conduction pathway

SA node → AV node → Bundle of His → bundle branches → Purkinje fibers

Cardiac cycle

Atria contract → ventricles contract → relaxation

What blood pressure measures

Force of blood on arterial walls

Systolic pressure

Ventricular contraction

Diastolic pressure

Ventricular relaxation

Atherosclerosis

Plaque buildup in arteries

Why atherosclerosis is dangerous

Narrows vessels; increases BP; risk of heart attack/stroke

Pulmonary veins return blood to

Left atrium

Small muscle masses attached to chordae tendineae

Papillary muscles

Source of blood to myocardium capillaries

Coronary arteries

Foramen ovale

Fetal opening between atria

Foramen ovale becomes

Fossa ovalis

Ductus arteriosus

Fetal vessel connecting pulmonary trunk to aorta

Ductus arteriosus becomes

Ligamentum arteriosum

Vessel receiving blood during right ventricular systole

Pulmonary trunk

When tricuspid valve is closed

During ventricular systole

Valve preventing backflow into left ventricle

Aortic valve

Fenestrated capillaries found in

Kidneys, endocrine glands, small intestine

Sinusoidal capillaries found in

Liver, spleen, bone marrow

Differences between arteries and veins

Arteries: thicker walls; Veins: valves, larger lumen

Mechanisms assisting venous return

Skeletal muscle pump, respiratory pump, venoconstriction

Nervous system innervating blood vessels

Sympathetic nervous system

Neurotransmitter released onto vessels

Norepinephrine

Hepatic portal system

Blood from digestive organs goes to liver before systemic circulation

Vessels in hepatic portal system

Portal vein, splenic vein, superior mesenteric vein

Flow of blood through liver

GI organs → portal vein → liver → hepatic veins → IVC

When fetal blood is oxygenated

In the placenta

When fetal blood is deoxygenated

After delivering oxygen to fetal tissues

Pacemaker cell action potential

Unstable resting potential; slow Na⁺ leak; Ca²⁺ influx causes depolarization

Myocardial action potential

Rapid Na⁺ influx → Ca²⁺ plateau → K⁺ repolarization

Importance of plateau

Prevents tetany; ensures full contraction

End‑diastolic volume (EDV)

Volume in ventricle after filling

End‑systolic volume (ESV)

Volume in ventricle after contraction

Stroke volume

EDV − ESV

Cardiac output

Heart rate × stroke volume

Effect of blood volume on BP

↑ volume → ↑ BP

Effect of viscosity on BP

↑ viscosity → ↑ BP

Effect of vessel diameter on BP

↓ diameter → ↑ resistance → ↑ BP

Effect of atherosclerosis on BP

Narrows arteries → increases resistance → increases BP

Why progesterone causes bloating

Causes water and sodium retention