anatomy and physiology module 3

arteries

carry blood away from the heart

capillaries

Microscopic vessel through which exchanges of nutrients and waste occur

venules

smallest veins that gather blood from the capillaries into the veins

veins

Blood vessels that carry blood back to the heart

tunica media

middle layer of artery; made up of smooth muscle fibers and elastic connective tissue

tunica media of muscular artery

thick; larger role in vasoconstriction

tunica intima of muscular artery

most interior layer composed of epithelial and connective tissue layers directly in contact with blood flow

arteriole

the smallest kind of artery

arteriole layers

tunica intima, tunica media, tunica externa but thicker

elastic arteries

Thick-walled arteries near the heart; >10mm

elastic arteries lumen

large diameter

elastic fibers

allow for expansion with blood sugars and recoil

recoil

maintains pressure gradient, drives blood through arterial system

muscular arteries

distribute blood to specific organs

arteriole leads to

capillaries

arterioles are critical for

slowing blood flow due to large pressure drops

arteriole vascular tone

remain slightly contracted

primary site of resistance and regulation of bp

arteriole

primary mechanism for regulation of blood distribution

arteriole

lumen

hollow passageway where blood flows

lumen in arteries

thicker walls, narrower

lumen in veins

wider, more blood flow, less resistance

vaso vasorum

small blood vessels that supply blood to the cells of the walls of the arteries and veins

What is the tunica intima?

The innermost layer of a blood vessel.

What type of cells compose the tunica intima?

A single layer of squamous epithelial cells.

What is found beneath the squamous epithelial cells in the tunica intima?

A sheet of connective tissue.

What is the function of the smooth surface of the tunica intima?

It allows blood to flow smoothly through the vessel.

what does the tunica intima release

endothelins

endothelins

local chemical messengers, construct blood flow, increase BP

appearance of tunica intimate in veins

smooth

appearance of tunica intima in artery

wavy

tunica Medina

Middle layer of an artery or vein

what is the tunica medina made up of

circular and longitudinal smooth muscle supported by connective tissue (collagenous fiber)

what occurs during vasoconstriction to tunica Medina

decreases diameter of lumen and blood flow

what occurs during vasodilation to tunica Medina

lumen widens, increases blood flow

external elastic membrane of tunica medina

present in larger arteries only

tunica externa is made up of

external collagen and elastic fibers, thick connective tissue, some elastic bands

capillary structure

Endothelial tube, inside thin basement membrane

No tunica media

No tunica externa

Diameter is similar to red blood cell

why are capillaries leaky

to facilitate diffusion, filtration, and osmosis

what do capillaries supply

supply blood to tissues

how big are capillaries

5-10 micrometers

types of capillaries

continuous, fenestrated, sinusoids

endosomes

carry and sort material brought into the cell

most common capillary

continuous capillary

all capillaries have tight junctions

true

tight junction of continuous capillaries

incomplete, intercellular clefts, selective permeability

where are continuous capillaries located

brain

fenestrated capillaries location

kidneys, endocrine glands, small intestine, choroid plexus(brain)

fenestrated capillaries in kidneys

filter blood

fenestrated capillaries in endocrine glands

hypothalamus and pineal glands

fenestrated capillaries in small intestines

nutrient absorption

what are fenestrations

pores in endothelial lining, permeable to large molecules, # and size vary by location

sinusoid capillaries

least common, flattened, large gaps bw adjacent cells

why does blood move slowly in sinusoid capillaries

more time for exchange of materials

location of sinusoid capillaries

bone marrow, lymph nodes, liver, spleen, endocrine glands (pituitary and adrenal)

capillary beds

a network of capillaries in a tissue or organ, enables tissue perfusion

precapillary sphincters

control the blood flow into capillary beds.

precapillary sphincters open

surrounding tissue need oxygen or have tissue waste

thoroughfare channel

precapillary sphincters are closed, blood travels from arterial to venule, bypassing capillary bed

arteriovenous anastomosis

direct connection between arteriole and venule

how are capillary beds regulated

internal conditions, chemical signals

walls of venues systems

much thinner than arteries

venule

the smallest kind of vein

where does diapedesis occur

post capillary venules

diapedesis

passage of blood cells (especially white blood cells) existing blood stream into the surrounding tissue

veins valves

one way, prevent backflow of blood, low pressure in veins

veins during muscle contraction

inferior valve closes, superior opens, blood moves towards heart

veins and venues are also known as

capacitance vessels

capacitance vessel function

can store high volumes of blood due to large lumens and thin walls with minimal change on bp

What is venoconstriction?

The narrowing of veins.

What type of control is venoconstriction under?

Sympathetic control.

What effect does venoconstriction have on blood flow?

It pushes blood toward the heart.

How does venoconstriction affect the shape of veins?

It stiffens veins and makes the lumen more rounded.

What happens to surface area during venoconstriction?

It causes a decrease in surface area.

What is the effect of decreased surface area on resistance and flow?

It increases resistance and decreaes flow.

What is the impact of venoconstriction on preload?

It increases preload or stretch on the cardiac muscle.

what is the vasomotor center

a cluster of sympathetic neurons in the medulla that oversees changes in blood vessel diameter and blood flow distribution

arterial anastomoses

provide alternate pathways (collateral channels) to ensure continuous flow, even if one artery is blocked

vascular anastomoses

Interconnections of blood vessels providing alternate pathways.

vascular shunts

ensure alternate circulation

vasoconstriction

constriction of artery, decreases radius, increases resistance, decreases flow

blood pressure is a form of

hydrostatic pressure

blood flow is directly proportional to the

pressure gradient

1 multiple choice option

blood flow is indirectly proportional to

resistance

1 multiple choice option

fluids will move

from areas of higher pressure to areas of lower pressure

peripheral resistance

the opposition to flow that blood encounters in vessels away from the heart

What factors affect peripheral resistance?

blood viscosity, vessel length, vessel radius, volume, turbulence

total peripheral resistance

the resistance of the entire cardiovascular system

factors of vascular resistance

friction between blood and vessel walls

What is blood viscosity?

thickness of blood due to formed elements and plasma proteins

increase of blood viscosity

increase resistance, decrease flow

vessel length is directly proportional to resistance

increase length and resistance, decrease flow

benefit of weight loss on vessel length

decrease vessel length, reduces stress on heart

vessels rarely decrease in length

true

Vessel diameter is inversely proportional to resistance

true

why is the vessel diameter able to change

in response to local or systemic changes

slight increase or decrease in vessel diameter

dramatic changes

velocity of blood flow is influenced by

heart rate, vessel diameter, TPR

largest influence of velocity

arterioles, resistance vessels

which vessels have the most significant role in BP regulation

arterioles, capillaries have smaller diameter and large cross-sectional area