Circulation

Question 1

Functions of Circulatory System

Answer 1

Transport blood and nutrients such as O2 to body

Remove waste like CO2

Question 2

The Heart (Location)

Answer 2

Within mediastinum behind sternum between points of rib attachment 2-6
Two thirds of mass is on the left of the midline of the body
Apex is bottom tip and points to left
Base is top and at 2nd rib

Question 3

Arteries

Answer 3

Carries blood away from the heart; all arteries except pulmonary artery carries oxygenated blood

Question 4

Elastic Arteries

Answer 4

Elastic arties are largest in the body (e.g. aorta and it’s major branches).
Stretch without injury, which allows them to accommodate the surge of blood when heart contracts
Able to recoil when ventricles relax

Question 5

Muscular Arteries

Answer 5

Distributing arteries
Smaller in diameter than elastic arteries
Thick muscular layer
Ex. Branchial, Gastric, Superior Mesenteric

Question 6

Arterioles

Answer 6

Resistance Vessels
Smallest Arteries
Important regulating blood flow to end organs

Question 7

Metarterioles

Answer 7

Short connecting vessel between true arteriole and 20 to 100 capillaries
Encircled by precapillary sphincters

Question 8

Thoroughfare Channel

Answer 8

On the distal end of the metarterioles

Free of pre capillary sphincters

Question 9

Capillaries

Answer 9

Primary site of gas and nutrient exchange
Microscopic in size so that only allows one red blood cell to go through at a time
Carry blood from the arterioles to the venules
They are not evenly distributed within the body with the greatest amount being in areas with a high metabolic rate (i.e. muscles)
In “avascular” tissues such as cartilage and bones capillaries may be absent

Question 10

Microcirculation

Answer 10

Together with the arterioles, capillaries and venules will make up the microcirculation

Question 11

Veins

Answer 11

Carry blood towards the heart
Act as collectors and reservoirs vessels
Called capacitance vessels as they have he capacity to take on large volumes of blood without rupture, they take on larger volume due to being more flexible
They are extensions of the capillaries as after capillaries they will unit into vessels then continue in size to form venues and then veins

Question 12

Tunica Externa

Answer 12

The outer coat that is found in aerties and veins and is also called the tunica adventitia

Question 13

Tunica Media

Answer 13

Middle layer found in both arteries and veins,

Question 14

Tunica Intima

Answer 14

Found in all blood vessels and is the innermost layer. It is the only layer of capillary cells (KNOW)

Question 15

Vessel Lining

Answer 15

Endothelial cells
Only layer in capillaries
Lines entire vascular tree
Provides smooth luminal surface in arteries (not as smooth in veins)
Protects against intravascular coagulation
Intercellular clefts, cytoplasmic pores, and fenestrations allows that exchange to occur between the blood and tissue fluid
Capable of secreting a number of substances
Capable of self reproduction

Question 16

Vessel Structures-Collagen Fibers

Answer 16

Formed from combined protein molecules 
Visible with a light microscope 
Limited ability to stretch (2-3%) under physiological conditions
Strengthen and keep lumen of vessel open
Exhibit woven appearance

Question 17

Vessel Structures-Elastic Fibers

Answer 17

Composed of elastin which is a insoluble protein
Forms highly elastic networks
Can stretch more than 100% under physiological conditions
Plays an important role in creating passive tension to help regulate blood pressure throughout the cardiac cycle

Question 18

Vessel Structure-Smooth Muscle Fibres

Answer 18

Present in all vascular (except capillaries) however there is very little in veins and more common in elastic and muscular arteries
exert active tension during contraction
Directly connected to autonomic nervous system

Question 19

Type of Capillary Linings

Answer 19

Continuous Capillary: The presence of clefts if only between adjacent endothelial cells. Provides an uninterrupted lining (ex. Blood brain barrier which does not allow a lot through)
Fenestrated Capillary: In addition to intercellular clefts, fenestrations (pores) exist in the plasma membrane of endothelial cells
Sinusoid: In addition to the large intercellular clefts and cellular fenestrations, the basement membrane is incomplete or absent (ex. Bone marrow and liver)

Question 20

End Arteries

Answer 20

Arteries that diverge into capillaries

Question 21

Arterial Anastomoses

Answer 21

Arteries that open into other branches of the same or other arteries
Incidence of arterial anastomoses increases as distance from the heart
Allows for collateral circulation which is importance as when we puncture the radial artery we can still have circulation to the hand

Question 22

Arterio-Venous Anastomses

Answer 22

Shunts
Occurs when blood flows from an artery directly into a vein (skips the capillary network)
There is an anastomoses at the base of the brain

Question 23

Veins Anastomoses

Answer 23

Veins that open into other branches of the same or other Veins
Incidence of vein anastomoses increases as distance from the heart
Allows for collateral circulation

Question 24

Where Do Veins Drain Into

Answer 24

Venous blood from the head, neck, and upper extremities will drain into the superior vena cava
Venous blood from the thoracic cavity and organ (except lungs) will drain into the superior vena cava or azygous vein
Venous blood from the lower extremities will drain into the inferior vena cava

Question 25

Hepatic Portal Circulation

Answer 25

Veins from the spleen, stomach, pancreas, gallbladder, and intestines will send blood to the liver via the hepatic portal vein In the liver the venous blood mingles with arterial blood in the capillaries and is eventually drained from the liver by the hepatic vein that will join the inferior vena cava