Vascular System Flashcards
What are the layers of a typical muscular blood vessel?
Tunica intima
Tunica media
Tunica adventitia
Tunica intima
Endothelium, sub-enthelium tissue with loose CT and capillaries, and internal elastic lamina
Tunica Media
Circularly arranged smooth muscle cells separated by collagen and elastic fibers
Tunica adventitia
Connective tissue
Adventitia in vessels with thick walls contain vasa vasorum that supply nutrients to the media of thick vessels
What are the 2 main systems in the body?
Blood circulatory and lymphatic
Blood circulatory/ Cardiovascular system
Transports O2, CO2, nutrients, waste products, defense cells, heat, blood cells and hormones around the body
Maintains pH and temperature
Lymphatic system
Transports tissue fluid, lymphocytes, and fats (gut) to the circulatory system
Absent in the CNS and bone marrow
What is structures are included in the systemic blood vessels?
Beginning from the heart, the vessels include elastic arteries, muscular arteries, arterioles, metarterioles, capillaries, venules and veins
what separates T. media and T. adventitia in larger muscular arteries?
External elastic lamina
Elastic artery characteristics
Internal elastic lamina inconspicuous
T. media: thick with elastic and smooth muscle cells
Ex: aorta and brachiocephalic trunk
What do elastic fibers do in elastic arteries?
Stretch duirng systole
Coil during diastole
Help maintain continuous flow in vessels during diastole
Artery layers classification
4 or more: muscular artery
1-3: arteriole
Arterioles
Smallest arteries with less than 0.1 mm in diameter and a narrow lumen
Internal elastic lamina present
T. media has 1-3 muscle cell layers
What is the function of the arteriole?
Regulate blood pressure
Metarterioles
Between arterioles and capillaries
Surrounded by an incomplete layer of smooth muscle (precapillary sphincters)
Precapillary sphincters
Contraction prevents blood from entering the capillaries
Open: blood moves from metarterioles to capillaries then to venules
Closed: blood bypasses capillaries, moves directly from metarterioles to venules
Capillaries
8-10 um in diameter
Endothelial layer, basal lamina, pericytes
3 types: continuous, fenestrated, and sinusoidal (discontinuous)
What is the function of capillaries?
Permit the exchange of gases, fluids, metabolites and other substances between blood and connective tissue
Continuous capillaries
Endothelial cells (continuous) with junctional complex between cells
Pinocytic vesicles in the cell cytoplasm
Continuous basal lamina and pericytes outside BL
Where are continuous capillaries located?
Nervous tissue, muscle, CT, exocrine glands and lungs
Fenestrated capillaries
Continuous basal lamina and endothelial cells
Wall perforated with fenestrate (60-80 nm)
Where are fenestrated capillaries located?
With a diaphragm: endocrine glands, intestine, pancreas
Without a diaphragm: glomerulus of kidney
Sinusoidal (discontinuous) capillaries
Larger than others, 30-40 um
Large fenestrations between edothelial cells
Discontinuous basal lamina
Where are sinusoidal capillaries found?
Liver, spleen, bone marrow, lymph nodes, adrenal cortex and anterior pituitary
Venules size
Postcapillary venules: 20-50 um
Muscular venules: 50-100 um
Venules characteristics
Endothelial layer
Basal lamina
Collagen fibers to 1-2 cells thick smooth muscle layer
What are the function of venules?
Exchange of metabolites and diapedesis (entry of leukocytes into the CT by squeezing through the intercellular junctions)
Veins vs. Satellite artery
Larger lumen, usually filled with blood, thinner T. intima and T. media, thicker T. adventitia
Venules vs. Arteriole
Venules have a larger lumen, a thinner wall, more blood cells in the lumen
Vein sizes
Small: up to 1 nm
Medium: 1-10 mm
Larger: more than 1 cm (vena cava and pulmonary)
Vein characteristics
Have T. media, intima and adventitia
Has valves
Large veins have smooth muscles in the adventitia
What is the function of arteriovenous anastomoses?
Blood goes to metarterioles to venules and bypass capillaries
Play an important role in skin’s thermoregulation
Valves
Two semilunar folds composed of CT rich in elastic fibers
Lined on both sides by endothelium
Veins Innervation
Supplies by sympathetic fibers that cause vasoconstriction
Some blood vessels have cholingeric sympathetic innervation capable of producing vasodilation
Lymph capillaries
Begin as blind-ended channels
Single layer of endothelial cells with or without fenestrations
Lack TJs
Discontinuous basal lamina
Function of lymph capillaries
Collect excess tissue fluid (lymph) and return it to the venous system
Lymph vessels
Possess valves and
Larger lumen and thinner walls than small vein
Enter lymph nodes before they empty into lymph ducts
Afferent entering node, efferent leaving node
Lymph ducts
Similar in structure to larger veins
T. media has longitudinal and circular smooth muscle cells
T. adventitia is poorly developed
Thoracic duct, right lymphatic duct
Usual sequence of blood flow
Heart –> elastic artery –> muscular artery –> Arteriole –> metarteriole –> capillary –> venule –> vein –> heart
Where are arteriovenous anastomoses present?
Skin, penis ovary
Where is an arterial portal system present?
Kidney glomerulus
Capillaries interposed between 2 arterioles
Afferent arteriole: gives rise to mass of capillaries
Efferent: gives ride to capillary networks (peritubular and vasa recta) surround nephrons
Where is a venous portal system present?
Liver, veins into capillary or sinusoid network draining into a vein
Vein interposed between 2 capillary networks
What are the 3 layers of the heart?
Endocardium, myocardium and epicardium
What is the heart innervation?
Sympathetic and parasympathetic
Heart impulse generating and conducting system
SA node (pacemaker)
AV node
Bundle of His (purkinje fibers)
Helical arteries
Subendothelial tissue has longitudinal smooth muscle cushion which helps regulate blood flow
Penis and uterus
Umbilical artery
T. muscularis has inner circular and outer longitudinal layer
Skull Arteries
Lamina elastica interna is very thick
T. muscularis is thin
Hepatic portal circulation
Capillaries - blood vessel - capillaries
Gut arteries–> capillaries –> portal vein –> liver sinusoids
–> hepatic vein
In liver and intestines
What are other portal systems of the body?
Hypothalamus- hypophyseal portal system
Renal portal (only in avian)
What are the 2 phases of the heart?
Contraction (systole)- active phase when energy expended
Relaxation (diastole)- resting phase
What forms the microcirculatory bed?
Arterioles, capillaries, post capillary venules
Portal system
Blood draining from capillary bed of one structure
Flows through larger vessels to supply the capillary bed of another structure then returns to the heart
Pericardium
Pericardial sac with serous percardium (parietal and visceral layer)
Epicardium
Visceral layer of pericardium
Provides support to the outside
What are the parts of the epicardium?
Mesothelium: provides serous fluid
Subepicardial: Loose CT and adipocytes, support, protect and insulate the heart
Endocardium
Endothelium and subendothelium CT
Sub CT tissues connect endocardium to myocardium
