Lecture 8 - Cardiovascular 1 Flashcards
Vasculature
3 types of blood vessels
Veins
Arteries
Capillaries
What direction do veins travel
Carry blood towards the heart
- deoxygenated blood in body / oxygenated blood in pulmonary
What direction to arteries travel
Carry blood away from the heart
- oxygenated blood in body / deoxygenated blood in pulmonary
What arteries are largest in body
Elastic
What are characteristics of elastic arteries
- able to stretch without injury
- accommodate surge of blood when heart contracts and can recoil when ventricles relax.
(Aorta and major branches)
What are the distributing arteries
Muscular arteries
What are characteristics of muscular arteries
Smaller in diameter than elastic arteries
- muscular layer is thick
(Brachial, gastric, superior mesenteric
What are the resistance vessels
Arterioles
Characteristics of arterioles
Smallest arteries
- important in regulating blood flow to organs
What are metarterioles
- short connecting vessel between arteriole and 20 to 100 capillaries (extends through capillary bed)
Characteristics of metarterioles
Circled by precapillary sphincters that can influence the volume of blood flow through the capillary
- distal end is calle thoroughfare channel and is free of precapillary sphincters
Which of the 3 artery types has the most fibrous tissue
Muscular artery
Which of the 3 artery types has the most elastic tissue
Elastic artery
Which type of artery has the least muscular tissue
Arteriole
What are capillaries
The primary exchange vessels between blood and tissue cells
Characteristics of capillaries
Microscopic vessels
- carry blood from arterioles to venules
- not evenly distributed in body
What constitutes the microcirculation
Arterioles, capillaries and venules
Where are there more capillaries
In tissue with high metabolic rate
Liver, cardiac muscle
Where are capillaries absent from tissue
In avascular tissue
- cartilage
- some types of epithelium
What happens when precapillary sphincters are relaxed
Permits blood flow to enter capillary bed
What happens when precapillary sphincters contract
Blood flows directly from metarteriole through thoroughfare channel (skipping capillary bed) going to venule
What are the 3 types of capillaries
Continuous capillaries
Fenestrated capillaries
Sinusoid
What is a true capillary
Capillary that receives blood from metarteriole with input regulated by precapillary sphincter
Characteristics of continuous capillaries
They have continuous lining of endothelial cells with openings called intercellular clefts between them
(Found in skeletal muscle, lung, connective tissue
Characteristics of fenestrated capillaries
They have intercellular clefts and fenestrations (holes) through plasma membrane to facilitate exchange functions
(In kidneys, small intestine)
Characteristics of Sinusoid capillary
- Large lumen and tortuous course
- Absent or incomplete basement membrane
- Very porus ,allows migration of cells through vessel lumen
- Found in bone marrow and liver
What is the ultimate extension of capillaries that unites with others of it kind in increasing size
Veins - unite to form venules then veins
What are the rural sinuses
Large veins of the cranial cavity
Do veins or arteries anastomose
Both
What is the superior vena cava
The vein that bring blood from head, upper extremities, and thoracic cavity (except lungs) to the heart right atrium
What is the inferior vena cava
The vein that bring blood from lower extremities and abdomen to the heart right atrium
Characteristics of venules
- Small diameter
- Closest to capillaries
- Fluid can be exchanged btw venules and tissue spaces
- phagocytic WBC can leave venules to get into inflamed tissue through pores
Characteristics of veins
Become progressively larger as additional blood flows into them / act as collector and reservoir vessels
Structural features of veins
- Great ability to stretch and accommodate varying amount of blood without changing BP
- Have one-way valves which keep blood flowing toward the heart and prevent backflow
What is capacitance vessel
Can contain much more blood than resistance vessel. Ability to stretch and retract when volume decreases
What is venous sinus
-Large venous structures
-Very thin walls
-No smooth muscle or support tissue in outer layer
-cannot change shape
Ex. Dural sinus of brain, coronary sinu of heart
What are capillaries primary relative tissue makeup
Tissue of endothelium
What are veins 2 primary tissue makeups
Smooth muscle and fibrous tissues
What are the 3 layers of blood vessels structure
Tunica externa
Tunica media
Tunica intima
What is structure and function of Tunica externa
- aka tunica adventitia
- made of strong flexible fibrous CT that prevents tearing of vessel walls during body movement
- collagen fibers extend from this layer to connect nearby structures
- anchors the vessel and helps hold it open
- thicker in veins
What is structure and function of Tunica media
- smooth muscle that permits changes in blood vessel diameter
- is innervated by autonomic nerves (nervi vasorum) and supplied with blood by tiny vasa vasorum- arteries have a thicker layer of smooth muscle than veins
What is structure and function of Tunica intima
- endothelium and base membrane
- capillary has only Tunica intima = thinness allows for efficient exchange of materials between blood plasma and the interstitial fluid surrounding the cells
What are the 4 building blocks of vessels
- Lining endothelial cells
- Collagen fibers
- Elastic fibers
- Smooth muscle fibers
Where are lining endothelial cells found
Line entire vascular tree and the only lining found in capillaries
How to lining endothelial cells protect against intravascular coagulation
By providing a smooth luminal surface
What do intercellular clefts and fenestrations do in lining endothelial cells
Allow exchange to occur between blood and tissue fluid
2 things lining endothelial cells are capable of
1 Secreting a number of substances
2 Reproduction
What is formation and appearance of collagen fibers
- formed from protein molecules that aggregate into fibers
- have woven appearance that is visible with light microscope
What is ability of collagen fibers to stretch
2 to 3% under physiological conditions
What is the function of collagen fibers
To keep lumen of vessel open and strengthen the wall ( does not help with tension or recoil)
What are elastic fibers composed of
Insoluble protein called elastin
What is stretch capability of elastic fibers
More than 100% under physiological conditions and allow for recoil after distension
What important role does elastic fibers play
In creating passive tension to help regulate BP throughout cardiac cycle
What is difference between passive and active tension
Passive is tension that is always there= elastic fibers that can passively recoil
Active tension is created tension = muscle fibers contracting
Where are smooth muscle fibers found
In all segments of vascular system except capillaries
- most numerous in elastic and muscular arteries
What is a function of smooth muscle fibers
Exerting active tension by vessels contracting
What is systemic circulation
Blood flows from left ventricle of heart through blood vessels to all parts of the body ( except lungs) and back to right atrium
What is pulmonary circulation
- Venous blood moves from R atrium to R ventricle to 2 pulmonary arteries to lung arterioles and capillaries, where gas exchanged
- Oxygenated blood returns to L atrium by 4 pulmonary veins then L ventricle
What are the 5 vessels blood goes through in veins
Arteries Arterioles Capillaries Venules Veins
General rule of thumb for circulatory routes
Blood passes through only one capillary network in the systemic circulation from the time it leaves the heart until it returns
What are the 2 exemptions to the general rule of circulatory routes
Portal system
Vascular anastomosis
What is the portal system
Blood flowing through the systemic circulation passes through 2 consecutive capillary beds rather than 1
What is vascular anastomosis
Direct connection of blood vessels to one another without passing through intervening capillary network.
Vein to vein
Artery to artery
Artery to vein
When does arterial anastomosis occur
May develop in response to disease
- allows bypass of blocked artery
Ex. In smaller coronary arteries allows collateral circulation of ischemic cardiac muscle tissue (but not in larger)
Ex. Palmer arches, plantar arch, circle of Willis
What does venous anastomosis do
More common type, Multiple venous routes from organs
- DVT can be prevented or lessened
Ex. Dorsal venous arches of hand and foot
What does arteriovenous anastomoses do
Aka shunts
Blood flows from artery to vein without passing capillary bed
Heat loss that would normally occur when passing through capillary bed in skin is kept in blood circulation to avoid heat loss during hypothermia
(Ex skin of nose, lips, external ear)
What way does blood circulate
Unidirectional
5 Types of circulation
Systemic Pulmonary Coronary Hepatic Fetal
What is hepatic portal
Heart -> intestine -> liver -> heart
Fetal circulation route
Heart mother -> placenta -> child -> child heart -> placenta -> mothers heart
What is coronary sinus
Where vena cava’s go into heart deoxygenated
What are comes after ascending aorta
Aortic arch
What beaches to the right of aortic arch
Brachiocephalic artery then:
R common carotid artery and R subclavian artery
What branches off to the left of aortic arch
L common carotid artery and L subclavian artery
Where does aortic arch continue into
Thoracic aorta
What comes after thoracic aorta
Abdominal aorta
What does aorta go through after thoracic aorta
Diaphragm opening (hiatus)
What are 2 main arteries that shoot off from abdominal aorta
Superior mesenteric artery and inferior mesenteric artery
What comes after abdominal aorta
L common iliac artery and R common iliac artery
What does external common carotid feed
Outside of skill, face etc
What does internal common carotid artery feed
Inside brain / skull and middle cerebral artery
Where does vertebral artery come from and go
From subclavian into back of skull and then to basilar
Where does blood from face brain skull go
Internal and external jugular vein then subclavian vein and brachicephalic vein into superior vena cava
Where do R and L common iliac veins go
Inferior vena cava
Hepatic and renal veins enter inferior vena cava in which cavity
Abdominal
What feeds into hepatic portal vein
Veins from spleen, stomach, pancreas, gallbladder, and intestines feed blood to liver by hepatic portal vein
Where does liver drain all the mixed blood
Hepatic veins then inferior vena cava
Why does blood detour from digestive system through liver
- Excess glucose can be removed by liver(stored as glycogen)
- Drugs can be metabolized/detoxified before reaching general circulation
Fetal circulation steps
- umbilical arteries (infants iliac arteries) carry blood to placenta to pick up O2
- blood oxygenated as mixed with mother blood
- umbilical vein brings oxygenated blood from placenta into inferior vena cava
What is foramen ovale
Opening in septum between R and L atria
