CH 20 Blood vessel

Hepatic portal system

- A specialized part of the vascular circuit - Picks up digested nutrients (spleen, pancreas) - Delivers nutrients to the liver for processing *2 capillary bed: 1st Stomach and intestine; 2nd liver

Pulmonary circulation

*Pulmonary trunk leaves right ventricle and divides into left and right pulmonary arteries *Superior and inferior pulmonary veins carry oxygenated blood into left atrium

During fetal development, is there a need for the pulmonary circuit? How does the developing heart by-pass the lungs and what happens to these structures after the infant is born?

- Fetus supply blood to placenta (O2 and nutrients obtained from uterus) - Fetus sends little blood to pulmonary circuit because respiratory system is the placenta (fetus lungs do not need much blood) - When newborn takes first breaths, lungs inflate. There is no longer high resistance in pulmonary vessels and lungs receive more blood - For first time, oxygenated pulmonary blood begins pouring into left atrium - umbilical transport blood between mother and fetus *Adaptations 1. Ductus Venosus: Shunt prevents blood from going to liver. Goes to vena cava instead 2. Foramen ovale: Takes blood from right to the left side directly without going to lungs 3. Ductus arteriosus: Goes directly to aorta and to body

What is the function of vascular anastomoses?

- Forms when vessels unite or interconnect - Organs receive blood from more than 1 arterial branch, and neighboring arteries connect with one another to form arterial anastomoses = Arterial anastomoses provide alternatative pathways or collateral channels, for blood to reach a body region

What is the function of the blood brain barrier.

- Regulates what substances enter the interstitial fluid of the brain - Capillaries have complete tight junctions •No intercellular clefts are present •Vital molecules pass through •Highly selective transport mechanisms •Not a barrier against oxygen, carbon dioxide, and some anesthetics

How does blood pressure and blood flow change within arteries, capillaries, and veins? CHECK 7

Arteries - The arteries, which are strong, flexible, and resilient, carry blood away from the heart and bear the highest blood pressures. Because arteries are elastic, they narrow (recoil) passively when the heart is relaxing between beats and thus help maintain blood pressure. The arteries branch into smaller and smaller vessels, eventually becoming very small vessels called arterioles. Arteries and arterioles have muscular walls that can adjust their diameter to increase or decrease blood flow to a particular part of the body. Capillaries - pressure of blood lower and steady. Capillaries are tiny, extremely thin-walled vessels that act as a bridge between arteries (which carry blood away from the heart) and veins (which carry blood back to the heart). The thin walls of the capillaries allow oxygen and nutrients to pass from the blood into tissues and allow waste products to pass from tissues into the blood. veins - Veins have much thinner walls than do arteries, largely because the pressure in veins is so much lower. Veins can widen (dilate) as the amount of fluid in them increases. Some veins, particularly veins in the legs, have valves in them, to prevent blood from flowing backward

Define the following: Arteries, capillaries, veins. What does a blue vs. red blood vessel represent?

Arteries - carry blood away from the heart (red). Have thicker walls and big muscle layer Capillaries - smallest blood vessels. The site of exchange of molecules between blood and tissue fluid. Single layer of cell. Single file of RBC passes through Veins - carry blood toward the heart (blue). Have larger lumen.

Aorta

Ascending aorta- arises from left ventricle branches: coronary arteries Aortic arch - lies posterior to manubrium Branches: brachiocephalic trunk, left common carotid, left subclavian arteries Descending aorta - Continues from aortic arch *Thoracic and abdominal aorta *Divides into right and left common iliac arteries

Describe the anatomy of the following capillaries: continuous and fenestrated.

Continuous - most common, occuring in most organs such as skeletal muscles, skin, and CNS. Tight junctions and desmosomes hold capillary cells together. Capillary strengthened by pericytes, spider-shaped stem cell whose thin processes form a spaced netork around the capillary Fenestrated - Joined by tight junctions and contain intercellular clefts. Also contain pores. These occur in high rates of exchange between small molecules (small intestine, kidneys, endocrine gland, membrane of joints)

What are the two different types of capillaries and their functions?

Continuous capillaries - most common, contain gaps of intercellular clefts that allow small molecules to pass into and out of the capillary Fenestrated capillaries - contain pores, occur where there are high rates of exchange of small molecules between blood and surrounding tissue fluid Sinusoid capillaries - wide and leaky, occur when there is an extensive exchange of large materials such as proteins or cells

How does material move out of the capillaries and into the interstitial tissue?

Diffusion - CO2 and O2 diffuse through endothelial cells Intercellular clefts - small molecules are exchanged here Fenestrations - pores in endothelial cells allow passage Pinocytotic vessels - Invaginate from plasma membrane and travel across endothelial cells, transporting dissolved gases, nutrients, and waste products into capillary

How do elastic arteries and muscular arteries maintain relatively constant blood flow and pressure?

Elastic - Large lumen allows to serve as low-resistance conduits for conducting blood. High elastin content of conducting arteries dampens the surge of blood pressure. The elastic elements expand in response to increase blood pressure. Muscular - By actively changing the diameter of the artery, this layer regulates the amount of blood flowing to an organ according to the needs of the organ. Smooth muscle of the tunica media is sanwiched between an internal elastic membrane that forms the outer layer of the tunica intima, and an external elastic membrane that forms outer layer of tunica media. These membranes help dampen pulsatile pressure produced by heartbeat.

What are the three different types of arteries and what are their functions?

Elastic arteries - Largest arteries near the heart-the aorta and its major branches - with diameters ranging from 2.5 cm to 1 cm. High elastin content dampens surge of blood pressure. Large lumen to transport blood under a lot of pressure. Muscular (distributing) arteries - Lie distal to elastic arteries, regulates amount of blood flowing to an organ, contains wave internal elastic membrane and external elastic membrane. More muscular layer. Arterioles - smallest arteries, Diameter of arterioles controlled by Local factors in the tissues and Sympathetic nervous system

Describe the following structures and their function: precapillary sphincter, true capillaries, metarteriole, through fare channel, intercellular clefts, tight junctions.

Precapillary sphincters - Smooth muscle cells that regulate the flow of blood to tissues according to that tissue's needs for oxygen and nutrients True capillaries - Branch mainly from arterioles and provide exchange between cells and the circulation. A vessel from capillary beds that merge into the thoroughfare channel and joins a venule metarteriole - a vessel that is intermediate between an arteriole and a capillary - from which branch true capillaries Throughfare channel - Metarteries continues into this channel, a vessel intermediate between a capillary and a venule Intercellular clefts - gaps of un-joined membrane. Small molecules can enter and exit tight junctions - Hold capillary endothelial cells together and block passage of small molecules

Describe the anatomy and the function of sinusoids, where are they found.

Sinusoids - Wide, leaky capillaries - Usually fenesrated and endothelial cells have fewer cell junctions - occur when there is an exchange of large materials between blood and surrounding tissue - large diameter and twisted course ensure blood slows when flowing through these vessels (bone marrow and spleen)

What are the three layers (tunics) found in a typical blood vessel?

Tunica intima - Innermost tunic of a vessel wall. It contains the endothelium (Simple squamous epithelium) decrease resistance of blood flow Tunica media - Consists of circularly arranged sheets of smooth muscle fibers. Vasoconstriction - contraction of smooth muscle cells decreases diameter of the vessel. Vasodilation - relaxation of the smooth muscle cells Tunica externa - Connective tissue that contains many collagen and elastic fibers

Compare and contrast the tunic composition between arteries (elastic, muscular, arterioles), capillaries, veins (venule, medium size, large size) and what is the general function of each tunic. CHECK

Tunica intima - reduces friction, simple squamous, and subendothelial layer (Aerolar CT) Tunica Media - Controls vasoconstriction and dialation. Smooth muscle and elastic fibers Tunica externa - Protects and anchors the vessels to the surrounding structures. Areolar CT and Collagen fibers. Arteries - all the tunics Capillaries - Only tunica intima Veins - missing or very little elastic tissue

What are the two mechanisms that allow the movement of blood through the veins?

Valves - flow of blood toward heart pushes cusps apart, opening the valve, and any backflow pushes cusps together, closing the valve Skeletal muscular pump - contracting skeletal muscles press against veins, forcing valves proximal to the area of contraction to open and propel blood toward the heart

Why do some veins have valves?

Valves keep venous blood moving in 1 direction; valves opened by blood flowing toward the heart and closed by backflow. Skeletal muscles press against vein and propel blood toward heart

Define the following: vasoconstriction, vasodilation.

Vasoconstriction - contraction of smooth muscle cells decreases diameter of the vessel Vasodilation - relaxation of smooth muscle cells

What are the three different types of veins? What is the general function of veins?

Venules - smallest veins, Smallest venules - called postcapillary venules. To collect blood from the capillaries and merge onto medium sized veins and then large veins. Medium-sized Veins -These veins range from 2-9nm in internal diameter which is comparable in size to muscular arteries. The tunica media is thin and contains like the elastic arteries few smooth muscle cells. The thickest layer is the tunica externa , which contains longitudinal bundles of elastic and collagen fibers. ************************************************Veins: Blood pressure lower than arteries. Take blood from capillaries toward heart. Tunica externa is the thicest tunic in veins. * ************************************************Large Veins - These veins include the include the superior and inferior vena cava. Larger lumen than arteries. Few muscle walls. All three layers of the tunica are present in large veins. They have a slender tunica media surrounded by a thick tunica externa which is composed of mixtures of both elastic and collagen fibers.