Chapter 21

Tunica Interna

Innermost layer, adjacent to lumen

Tunica media

Middle layer of smooth muscle and elastic fibers, allowing arteries to regulate their diameter

Tunica externa

Outermost layer, adjacent to surrounding tissue

Elastic arteries (conducting arteries)

Large-diameter vessels with more elastic fibers, functioning as pressure reservoirs

Muscular arteries (distributing arteries)

Medium-diameter vessels that use smooth muscle to distribute blood to specific body parts

Anastomosis

the union of two or more arteries supplying the same region, providing an alternate route for blood flow

End Arteries

Only 1 artery supplies something, if blocked then fucked

Capillary walls

single layer of squamous cells, thin enough to allow exchange of nutrients and wastes between blood and tissue cells

Continuous capillaries

the most common type, with a sealed wall that only allows small substances through. muscles + lungs

Fenestrated capillaries

have small pores in the wall, allowing more substances to pass through quickly. kidneys + small intestine

Sinusoid capillaries

have large gaps in the wall, allowing even large substances like proteins and blood cells to pass through. liver + bone marrow

Venules

small vessels that are formed by the union of several capillaries

Veins

formed from several venules, has thinner tunica interna and media but a thicker tunica externa then arteries. (less elastic + smooth muscle)

Varicose veins (varicosities)

formed when venous valves become weak or damaged (looks twisted)

Venous Valves

structures in veins that prevent backflow

Spider veins

same thing as Varicose but in Venules

Blood Distribution

largest portion of blood is in Veins and Venules

Diffusion in Capillaries

Small nonpolar substances like O2 and CO2 pass directly through, while larger polar substances like glucose and a.a require facilitated diffusion

Simple diffusion

substances move freely on their own from high to low concentration, no help needed

Facilitated diffusion

substances are too large to pass through on their own, so they use a protein channel as a "door" to get through

Transcytosis

Endocytosis + Exocytosis, used for large lipid insoluble molecules for capillary exchange

Bulk flow

exchanges fluid by pushing around higher to lower pressure differences using Filtration + Reabsorption

Filtration

when pressure high pushes fluid and dissolved substances out of the capillary into the surrounding tissue (BHP + IFOP)

Reabsorption

when pressure low fluid and dissolved substances go back into the capillary from the surrounding tissue (BCOP + IFHP)

BHP + IFOP

the Blood hydrostatic pressure and Interstitial fluid osmotic pressure pushing shi out of capillary

BCOP + IFHP

the Blood colloid osmotic pressure and Interstitial fluid hydrostatic pressure that put shi into the capillary

Blood flow

mL/min

Cardiac Output (CO)

The volume of blood pumped by the heart per minute

Blood Pressure

Blood pressure is affected by cardiac output, blood volume, and vascular resistance

Mean arterial pressure (MAP)

= CO x resistance (R)

> the BV ↑ the BP

Cardiac Output Equations

CO = heart rate (HR) × stroke volume (SV)

CO = mean arterial pressure (MAP) ÷ resistance (R)

Mean Arterial Pressure (MAP)

The avg BP in the arteries throughout one complete heartbeat

Vascular Resistance

How difficult (resistance) it is for blood to flow through a vessel.

3 Factors of Vascular Resistance

Vessel size — smaller vessel = harder to flow through

Blood thickness — thicker blood = harder to push through

Vessel length — longer vessel = more friction = harder to flow through

Systemic vascular resistance (SVR)/total peripheral resistance (TPR)

total resistance of every single blood vessel in your entire body added together

Venous Return

volume of blood flowing back to the heart through the systemic veins

3 Factors of Venous Return

Relax/Contract Heart — suction from heart relaxing pulls blood in

Skeletal muscle pump — muscles squeeze veins pushing blood toward heart

Respiratory pump — breathing in creates suction that draws blood toward heart

Velocity of Blood Flow

Blood velocity decreases as total cross-sectional area increases, and increases as it decreases

CO = HR × SV

Cardiac output = how fast heart beats × how much blood per beat

If HR or SV goes up, CO goes up

CO = MAP ÷ R

Cardiac output = blood pressure ÷ resistance

More resistance = less blood flow

MAP = CO × R

Blood pressure = cardiac output × resistance

If CO or R goes up, blood pressure goes up

Medulla Oblongata

Contains Cardiovascular Center

Cardiovascular center

A group of neurons in the medulla oblongata that regulate heart rate, contractility, and blood vessel diameter

3 Sensory receptors input to Cardiovascular Center

Proprioceptors (joint),

Baroreceptors (BP),

Chemoreceptors (Blood acidity, H+, CO2, O2)

3 Sensory receptors output to Cardiovascular Center

Vagus nerve (para, slows heart),

cardiac accelerator (sympathetic),

vasomotor nerve (sympathetic constrict vesssels)

Baroreceptors

Sensory neurons that detect stretching in blood vessel walls and atria. Found in carotid sinuses + aorta

Vasoconstriction

(increases BP) → caused by Angiotensin II, ADH, norepinephrine, epinephrine

Vasodilation

decreases BP) → caused by ANP, epinephrine, nitric oxide

Increase blood volume

Aldosterone (sodium) and Antidiuretic (heart)→ they make kidneys hold onto water, keeping more fluid in blood

Decrease blood volume

(decreases BP) → Atrial Natriuretic Peptide — makes you pee more, reducing fluid in blood

Autoregulation

tissues can control their own blood flow without needing the brain to tell them what to do (caused by Physical and chemical stimuli)

Systolic BP

First sound heard

Diastolic blood pressure

Last sound heard

Shock

failure of the cardiovascular system to deliver enough oxygen and nutrients to meet the metabolic demands of body cells

Hypovolemic shock

dangerously low blood volume due to blood or fluid loss

Cardiogenic shock

heart fails to pump enough blood to meet the body's needs

Vascular shock

excessive vasodilation causes blood pressure to drop critically low

Obstructive shock

physical blockage prevents blood from flowing properly through the heart or vessels