A&P 2 Lecture Notes - Blood Vessels, Hemostasis, and Coronary Circulation

This set covers vascular anatomy (tunicas), blood pressure physiology, the process of hemostasis, and the mechanisms of coronary circulation and cardiac auto-rhythmicity.

Tunica interna (intima)

The inner layer of a blood vessel that faces into the lumen; it is made of simple squamous epithelial tissue called endothelium.

Tunica media

The thickest middle layer of blood vessels made of smooth muscle under involuntary (autonomic) control.

Tunica externa

The superficial blood vessel layer made mostly of connective tissue with collagen and elastic fibers that anchors the vessel to surrounding tissues.

Vasoconstriction

The contraction of smooth muscle in the tunica media which decreases the vessel diameter.

Vasodilation

The relaxation of smooth muscle in the tunica media.

Hemostasis [Ca2+] Range

The optimum calcium ion range required for blood clotting, which is $9-11\,mg/100\,mL$ of blood.

Arterial Baroreceptors

Specialized sensory neurons (stretch receptors) stimulated by the stretching or relaxing of arterial walls due to blood pressure changes.

Aneurysm

A localized region where an artery wall balloons out due to blood seeping between layers through rips or tears in the endothelium.

Aorta

The largest artery in the body, normally measuring $2.54\,cm$ ($1\,inch$) in diameter.

Blood Reservoir

A unique function of veins due to their ability to distend and hold large volumes of blood.

Skeletal Muscle Pump

The milking action of movement where skeletal muscles squeeze nearby veins to push blood toward the heart.

Diastole

The time in the cardiac cycle when both atria are filling with blood, representing the bottom blood pressure number (e.g., $70\,mm\,Hg$).

Systole

The time in the cardiac cycle when both ventricles contract, representing the top blood pressure number (e.g., $120\,mm\,Hg$).

Hypertension

A disease known as the "silent killer" where blood pressure stays elevated above $140/90\,mm\,Hg$.

Hemostasis

A normal, localized process of repairing blood vessels using five sequential steps to prevent excessive leaking.

Coagulation

A multi-stepped process involving the activation of $20$ clotting factors to form a fibrin mesh that traps red blood cells.

Fibrinolysis

The final step of hemostasis where the temporary clot is enzymatically digested as new tunicas seal the hole.

Deep Vein Thrombosis

An abnormal condition where blood clots do not get broken down and can travel to the heart and lungs.

Hemophilia A

An inherited bleeding disorder caused by a non-functioning Clotting factor VIII.

Coronary Sinus

A large vein on the posterior surface of the heart that converges deoxygenated blood from coronary veins and dumps it into the right atrium.

Anastomoses (Collateral Vessels)

Back-up branches of coronary arteries that diverge to provide alternate pathways for oxygenated blood.

Auto-rhythmic Fibers

Specialized cardiac cells (~$1$%) that spontaneously generate action potentials to initiate heart contractions internally.

Sinoatrial (SA) Node

The natural pacemaker of the heart that begins the electrical signal for contraction.

Vagus Nerve (Cranial Nerve X)

An extrinsic control that slows the SA node down and decreases the heart rate.