Histo 2 Flashcards
Tunica Intima
- Endothelium
- Basal Lamina
- Subendothelial Layer
- single layer of squamous epithelial cells
- thin EC layer (collagen, proteoglycans, glycoproteins)
- consists of loose areolar CT
a. Links endo layers to others
b. Internal Elastic Membrane: sheet like layer of fenestrated elastic material within arteries and arterioles
Tunica Media
- layers of smooth m.
- extends from internal to external elastic membrane (layer of elastin that separates the tunica media and adventitia)
- varying amounts of elastin, reticular fibers, and proteoglycans
What’s the thickest layer in the arteries? veins?
- Tunica Media
3. Tunica Adventitia
Tunica Adventitia
- longitudinally arranged collagenous tissue with few elastic fibers
- merges with loose CT surrounding the vessels (adheres to other structures like nerves
What are/where do we find vasa vasorum and nervi vasorum?
- Tunica Adventitia (large As and Vs); supply blood to the vascular walls to themselves
- Tunica Adventitia; ANS input that controls contraction of vascular smooth m.
Key features of Large Arteries
- elastin forms concentric sheets/lamellae between muscle layers (lamellae increase with age)
- NO fibroblasts
- smooth m synthesizes collagen, elastin, ground substance of ECM
- strong pressure of systole expands the arterial walls
- expanded lumen size reduces pressure, and allows strong blood flow to continue during diastole
Key features of Medium Arteries
- more smooth m and less elastin
- smooth m is arranged in a spiral fashion, and produce ECM components
- thick tunica adventitia (about same size as tunica media)
*Prominent internal elastic membrane
Key features of Small Arteries
- up to 8 layers of smooth muscle in tunica media
- internal elastic membrane
Key features of Arterioles
- 1-2 layers of smooth muscle in tunica media
- may or may not have internal elastic membrane
- function as flow regulators for capillaries
Key features of capillaries
- site of metabolic exchange
- diameter is often smaller than RBC
What are/where do we find perictyes?
- perivascular contractile cells with branching cytoplasmic processes (enclosed in BL, and continuous with endothelium)
- Controlled by NO to promote stability of capillaries and post capillary venules
What is the innermost aspect of the tunica media made of ?
single layer of endothelial cells
- connected via gap junctions
- support the basement membrane and produce collagen
- metabolically involved in blood coagulation and thrombosis (local vasoconstriction/dilation)
What are the 3 types of capillaries?
- Continuous
- Fenestrated
- Sinusodal
How does molecular exchange occur in the three types of capillaries?
- Continuous: diffusion or transcytosis
- Fenestrated: limited by size
- Sinusoidal: open exchange
Where do we find the three types of capillaries?
- Continuous: throughout body
- Fenestrated: endocrine glands, sites of fluid/metabolism absorption (gallbladder, kidneys)
- Sinusoidal: bone marrow, liver, spleen
What are met arterioles?
first branch off of arteriole supplying tissues
What are precapillary sphincters?
regulate blood flow through true capillaries (can be open or closed to allow/not allow blood flow)
What are true capillaries?
branch from metarteriole, lack smooth m., may have pericytes
What are thoroughfare channels?
distal end of metarteriole (no smooth m); connect to to post capillary venule
What happens when precapillary sphincters contract?
- they shunt blood flow, and prevent exchange within true capillaries
- blood is forced to enter venous return more quickly
Key features of venules
- receive blood from capillaries
- subclasses: post capillary (no true tunica media) and muscular venules (1-2 layers of smooth m., thin tunica adventitia)
Key features of small veins
- continuous with muscular venules
- all three tunica layers
- tunica media is 2-3 layers, and have thicker tunica adventitia
Key features of medium veins
- diameter of up to 10mm
- travel with muscular arteries
- thicker tunica media and adventitia
- contains valves
Key features of large veins
- diameter of greater than 10mm
- tunica adventitia:
a. the thickest layer
b. contains collagen, elastic fibers, and fibroblasts
c. contains longitudinal smooth m cells - tunica media:
a. thin with circumferentially arranged smooth m. cells, collagen fibers, and some fibroblasts - tunica intima:
a. thin
b. blends with tunica media
What tunica may contain valves?
intima
Between arteries and veins: who has the larger lumen? thinner walls? commonly collapsed lumen?
- vein
- vein
- vein
*hallmarks of the veins
Key features of Lymphatic Vessels
- collect lymph, and return it to venous supply
- serve as adjuncts to the BVs
- unidirectional
- contain all three tunics and posses valves
- tight junctions to repent leakage
*hallmarks: extremely thin; no blood in the lumen
Key features of Lymphatic Capillaries
- closed ended tubes found amount capillary beds
- have one way valve to collect lymph
- incomplete basal lamina to increase permeability
What is the role of anchoring filaments in lymphatic capillaries?
hold opening between endothelial cells in place (collapse to prevent back flow)
Lymph flow…
capillaries—>vessels–>trunks–>right lymphatic duct—>thoracic duct—>brachiocephalic v.
