Chapter 29 Flashcards
Nearly ______ km of blood vessels carry blood throughout the body
100,000
Angiogenesis
Formation of blood vessels begins during embryonic development and continues throughout life
Types of blood vessels (3)
Arteries, capillaries, veins
Arteries
carry blood away from the heart ventricles
All carry oxygenated blood EXCEPT pulmonary artery
aorta is largest one arteries (elastic and muscular) arterioles metarterioles that end at precapillary sphincters that wrap around entrance to capillaries (controls blood flow in to capillary beds)
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Capillaries
Microscopic blood vessels = microcirculation
site of gas and nutrient exchange between blood & tissue fluid around cells (capillary beds/networks); over 1 billion with highest concentration in tissues with high metabolic rate
connect arteries and veins via arterioles and venules
Veins
carry blood toward the heart atria
superior and inferior vena cava are the largest ones
Capillary beds/networks venules veins vena cava
Microcirculation
Heart-> aorta-> arteries-> arterioles-> capillary bed/network-> venules-> veins-> superior vena cav-> heart
4 types of materials that make up the wall of blood vessel
Endothelial tissue/ endothelium (lining)
Collagen fibres
Elastic fibres
Smooth muscle tissue
Endothelial tissue/ endothelium
Provides the lumen of blood vessels with a smooth surface, thereby influencing blood flow and intravascular blood clotting
A special type of simple squamous epithelium; allows for exchange of gases, nutrients, and other substances
Intercellular clefts between the cells and ‘fenestrations’ dictate movement of substances in and out of the blood vessel (See Figure in Textbook)
Collagen fibers
Provide blood vessels with strength and some flexibility (much less than elastic fibres)
Function to keep the lumen of blood vessels open
Strengthen blood vessels walls
Elastic fibres
Made of a protein polymer called ‘elastin’ - can stretch more than 100% when at work in the body
Arranged concentrically in large elastic arteries, allowing for distention and recoiling
Maintain passive tension of blood vessels for normal blood pressure
Smooth muscle tissue
Found in the wall of all blood vessels EXCEPT capillaries
Highest concentration is in elastic and muscular arteries contraction active tension
Tunica intima
Inner layer
Single layer of squamous epithelial cells (endothelium- lines entire surface of circulatory system)
One way valves
Tunica media
Middle layer
Smooth muscle with a thin layer of elastic tissue
Thicker in arteries than veins (to withstand systole)
Important in BP regulation (smooth muscle – ANS)
Tunica adventitia/externa
Outermost layer/collagen fibres
Reinforces wall of vessel to withstand pressure
Thicker in artery than in veins
Capillaries
Connect venules and arterioles
Only layer is the tunica intima
Extremely thin
Flat epithelial cells
Allows substances to quickly pass through wall
Arteries/ arterioles
move blood from heart to capillaries
distribution of nutrients, gases, etc., with movement of blood under high pressure
assist in maintaining the arterial blood pressure by constricting/dilating
Veins/venules
collect blood from capillaries for return to the heart
low-pressure vessels, so can act as reservoirs
e.g. can expand to hold a larger amount of blood
Capillaries
Serve as exchange vessels for nutrients, wastes and fluids for every body cell
Types of circulation (4)
Systemic circulation
Pulmonary
Hepatic portal
Fetal
Carries blood through out body
LV Aorta Smaller arteries Arterioles Capillaries Venules Veins Venae cavae RA
Pulmonary circulation
Carries blood to/from lungs
Arteries deliver deoxygenated blood to lungs for gas exchange
Hepatic circulation
- Unique blood route through the liver
- Blood from veins from spleen, stomach, pancreas, gallbladder and intestines does not go directly into inferior vena cava
- Blood gets sent to the liver via hepatic portal vein
- Blood passes through liver before re-entering regular venous return to heart via hepatic veins that drain into inferior vena cava
Venous blood (that would normally be sent back to the heart) is sent through a second capillary bed in the liver before returning to ‘normal’ pathway of blood returning to heart
- hepatic portal vein exists between two capillary beds
- one capillary bed is in the digestive organ
- one capillary bed is in the liver
Assists with:
- homeostasis of blood glucose levels - liver cells store excess glucose as glycogen
- detoxification
Fetal circulation
Refers to circulation before birth Modifications required for fetus to efficiently secure oxygen and nutrients from maternal blood instead of its own lungs and organs which aren’t fully developed or functional Unique structures of fetal circulation include: umbilical arteries (umbilical cord) Placenta umbilical vein (umbilical cord) ductus venosus foramen ovale ductus arteriosus
Umbilical arteries
2 small umbilical arteries that carry oxygen-poor blood from the developing fetus to the placenta
Placenta
Attached to uterine wall
Site of exchange of oxygen, nutrients, toxins and waste products between maternal and fetal blood
Umbilical vein
One umbilical vein (larger than the umbilical arteries) carries oxygen-rich blood from the placenta to the fetus
Gives of 2 or 3 branches at the fetal liver, then continues as the ductus venosus
Ductus venosus
A continuation of the umbilical vein along the undersurface of the fetal liver.
Shunts most of the blood returning from the placenta to the fetus past the fetus’ immature liver into the inferior vena cava
Foramen ovale
An opening in the interatrial septum
Shunts blood from the RA directly into the LA
Allows most of the blood to bypass the fetus’ underdeveloped lungs
Ductus arteriosus
Connects the pulmonary artery/ trunk with the aortic arch
Allows another portion of the blood to bypass the fetus underdeveloped lungs and enter systemic circulation
Changes in circulation at birth
As soon as the cord is cut, the vessels in the umbilical cord (e.g. umbilical arteries and umbilical vein) no longer function umbilical vein becomes the round ligament of the liver
The placenta is expelled after the baby is born
The ductus venosus becomes the ligamentum venosus of the liver
The foramen ovale functionally closes soon after the baby takes its first breath, which establishes pulmonary circulation; structural closure takes up to 9 months fossa ovalis in the wall of the right atrial septum
The ductus arteriosus contracts as soon as breathing starts ligamentum ateriosum
