BIO TEST #6 - Circulatory System and Lymphatic System

what are the three types of blood vessels within the circulatory system and what do they do

1.arteries (and arterioles) carry blood away from the heart to the capillaries 2.capillaries that permit the exchange of material with the tissues

3.veins (venules) return blood form the capillaries to the heart

what do all three blood vessels in the circulatory system have in common

an inner endothelium- a simple squamous epithelium attached to a connective tissue basement membrane that contains elastic fibres

what is the biggest artery in the body and why?

aorta- it carries O2-rich blood from the heart to other parts of the body

what does the wall of arteries (arterial wall) consist of

three layers- inner layer is endothelium, middle layer is the thickest and consists of smooth muscle that can contract to regulate blood flow and pressure, and outer layer is fibrous connective tissue

what are arterioles?

small arteries that branch off from the aorta

what are the three layers of arterioles

inner layer of endothelium, middle layer has some elastic tissue but mostly smooth muscle with fibres that encircle it, and an outer layer of fibrous connective tissue

what does the smooth muscles in arterioles do

when they relax, the vessel has a larger diameter (is dilated) and lower blood pressure results, when they contract there is a higher blood pressure

what are capillaries

narrow blood vessels that join arterioles to venules

what are capillaries made of

thin walls composed of a single layer of epithelium with a basement membrane

what do capillaries form throughout the body

vast networks called capillary beds

why does a cut to almost any blood tissue draw blood?

because capillary beds are present in nearly all regions of the body

since capillary beds have a total surface area of 6000m², is there any region that is nearly capillary free?

yes, the cornea of the eye is so that light can pass through

since the cornea of our eyes dont have capillaries, how do they obtain nutrients?

by diffusion from tears and from fluid on the inside surface

why do capillaries play an important role in homeostasis

because an exchange of substances takes place across their walls

what diffuses out of capillaries?

oxygen and nutrients like glucose along with some water that is picked up by lymphatic vessels

what diffuses into the capillary?

wastes like carbon dioxide

what is an example of capillary beds only being open at a given time

after eating, capillary beds that serve the digestive system are open, and those that serve the muscles are mostly closed

what controls the opening or closing of capillary beds?

sphincter muscles that relax to open the bed and allow blood flow or contract to close the bed and prevent blood flow

when sphincter muscles contract and close off the bed, can blood still get through?

yes blood can flow through anastomoses or arteriovenous shunts directly from arterioles to venules

how does blood flow straight through the anastomoses

precapillary sphincter muscles prevent blood from entering the capillary vessels

what do veins and venules do

they take blood from the capillary beds to the heart

what takes blood away from the capillary beds first?

venules (small veins) drain blood from the capillaries and then join to form a vein

what is the structure of veins and venules (they have a thinner wall than arteries)

they have the same three layers as arteries but there is less smooth muscle and connective tissue

what do veins that carry blood against the force of gravity have

valves that allow blood to flow toward the heart when open and prevent blood from flowing backward when closed

what would happen if these valves get damaged by disease or old age

blood can begin pooling in the veins, causing them to enlarge and cause varicose veins

how is blood flow different in the arteries & arterioles vs veins

blood flow in arteries is kept moving my the pumping of the heart while blood flow in veins is from skeletal muscle contraction

why are veins known to act as a blood reservoir?

since their walls are thinner, they can expand to a greater extent. 70% of blood is in the veins

how are veins helpful when we loose blood from bleeding?

nervous stimulation causes veins to constrict which provides more blood to the rest of the body

what are the largest veins in the body?

the vena cave (superior and inferior) which deliver O2-poor blood to the heart

what is blood

a liquid connective tissue that has many different functions

list the many different functions of blood (6)

transports nutrients, wastes, and hormones, regulates body temperature by dispersing body heat, regulates blood pressure from plasma proteins contributing to osmotic pressure of blood, protects against invasion by disease-causing pathogens, clotting mechanisms protect body against blood loss, and buffers in blood maintain its pH of 7.4

if blood is collected from a person’s vein into a test tube and centrifuged to prevent it from clotting, what would we see?

three layers- upper layer of plasma (liquid portion of blood), lower layers of formed elements like white blood cells and platelets (middle layer) and red blood cells (blood cells

what is plasma made of? (makes up 55% of our blood)

a variety of inorganic and organic substances dissolved or suspended in water

what makes up 7-8% of plasma

plasma proteins

what are the various functions of plasma proteins

transporting large organic molecules in blood like albumin transports bilirubin and lipoproteins transport cholesterol, blood clotting through fibrinogen, fighting infection through antibodies like immunoglobulins, and maintaining blood volume since plasma proteins are too large to leave the capillaries

why does water automatically diffuse into capillaries

because blood in capillaries has a higher solute concentration than tissue fluid

what are red blood cells (45% of our blood)

also called erythrocytes, they are made in the red bone marrow of the skull, ribs, vertebrae, and ends of the long bones that transport oxygen and carbon dioxide in the blood

describe the structure of mature red blood cells

they have no nuclei and are biconcave which increases flexibility for moving through capillary beds and increases surface area for diffusion of gases

why do red blood cells carry oxygen?

they contain hemoglobin which is a red respiratory pigment that also contains iron which acquires oxygen in the lungs and releases it in the tissues

where is iron found in a hemoglobin molecule?

in the four polypeptide chains in which each is associated with heme which is a complex iron-containing group

what does the lifecycle of a red blood cell look like

dies after 120 days and is destroyed in the liver and spleen where they are engulfed by large phagocytic cells. the iron is salvaged and reused while the heme undergoes chemical degradation and the liver releases it into bile as bile pigments

what is a common blood disorder that occurs when the body has an insufficient number of red blood cells or the red blood cells do not contain enough hemoglobin?

anemia occurs that can result in a tired, rundown feeling

what are the three basic causes of anemia

decreases production of red blood cells, loss of red blood cells from the body, and destruction of red blood cells within the body

what is the most common type of anemia

iron-deficiency where red blood cell production is decreased from a diet that lacks iron

what happens when arterial blood carries less oxygen like from chronic anemia

the kidneys release erythropoietin which speeds up red blood cell production in the bone marrow