blood vessel histology Flashcards
What are the layers of the blood vessels?
Tunica intima
Tunica media
Tunica adventitia
- elastic membrane between TI and TM in artery
How are impulses propagates through the smooth muscle?
Via gap junctions
What stimulates contraction in a vessel smooth muscle?
Postganglionic unmyelinated sympathetic fibers via NE
what color is elastin of the arterial walls in gross specimens?
yellowish
Which arteries have elastic (conducting)?
Aorta Common carotid Subclavian Iliac arteries Pulmonary trunk
What are the 3 characteristics of elastic conducting arteries Tunica intima?
- Endothelium
- Narrow layer of underlying CT
- Internal elastic lamina
What are Weibel-Palade bodies and where are they found?
Storage granules. Store and release von Willebrand factor and P-selectin
-Found in endothelium of elastic conducting arteries
How are the endothelial cells orientated and what connects them?
Elongates and orientated in longitudinal plane
-Connected by occluding junctions
What are fenestrated lamellae and where are they found?
Holes or sheets of Swiss cheese found in the Tunica media
- Give histo view a wavy look
What produces the ECM in tunica media?
Smooth muscle cells
What are some other characteristics of tunica media?
Very few fibroblasts
- Circularly arranged smooth muscle bundles alternate with elastin
- Fenestrate lamellae
What are some characteristics of tunica adventitia?
Relatively thin
Contains vasa vasorum
What is vasa vasorum?
Blood vessels of blood vessels
-Capillary beds spring from these vessels to supply the tunica media
What is the chief characteristic of muscular (distributing) arteries?
Thick tunica media comprised primarily of smooth muscle cells
What are the characteristics of muscular arteries tunica intima?
Thinner than elastic arteries
-Prominent internal elastic lamina (undulating contour)
How many layers can a muscular arteri tunica media smooth muscle be?
3-40
How are the smooth muscle cells arranged and is there elastic lamina present in muscular arteries tunica media?
Circumferentially
Yes
What produces the CT components of tunica adventitia of muscular arteries?
Fibroblasts
What are some other characteristics of muscular arteries tunica adventitia?
Vasa vasorum present
- Unmyelinated nerve endings
- Some thing elastic laminae
As arteries get smaller does the elastin increase or decrease?
Decrease
What is he average of of arterioles
What are the the layers of an arterioles?
Intima has endothelial cells, thin CT and sometimes thin elastic lamina
- Media- 1-3 layers of SM
- Adventitia is scant but produced by fibroblasts
What are metarterioles
Specialized structures that control blood flow into capillary bed by encircling the arteriole just proximal to where the capillary arises from the arteriole
What are 2 characteristics of metarteriolese SM cells?
Not continuous
-Act as sphincters by contracting (thus limiting the amount of blood let into the capillary)
What is the carotid sinus?
Baroreceptor found in the wall of the carotid arteries (at the bifurcation of common carotid)
What is thick in the carotid sinus and how is it innervated?
Adventitia
-Sensory fibers of glossopharyngeal
Is the tunica media thick or thin in the carotid sinus?
Thin
-Blood vessels distend with increasing blood pressure which stimulates the nerve
What are the carotid bodies?
Chemoreceptors at the bifurcation of the common carotid
-Nerve ending that monitor changes in O2, Co2 and hydrogen ions in blood
What is the the carotid bodies innervated by?
Afferents are 9 and 10
What are aortic bodies? Where are they?
Chemoreceptors
-Aortic arch between right subclavian and right common carotid and between left common carotid and left subclavian
What is the diameter of a typical capillary?
8-10 microns
-RBC is about 7
What are some characteristics of capillaries?
Single layer of elongated simple squamous endothelial cells
- External surface has basal lamina
- Vimentin and desmin
- Pinocytotic vesicles ass with cell membrane
What joints capillaries together?
Fascia occudentes
What are pericytes and there relationship with capillaries?
Provide structural support and can contract to control capillary diameter
- May give rise to SM and endothelial cells
- Sometimes form gap junctions with endothelial cells
- On caps and small venules
What body systems have continuous capillary types?
- Muscle
- CT
- CNS
What body systems have fenestrated capillary types?
- Kidney glomeruli
- Endocrine glands
- Intestinal villi
- Exocrine pancreas
What body systems have sinusoidal capillary types?
- Liver
- Spleen
- Bone marrow
- Lymph nodes
What are the 3 types of capillary types?
- Continuous
- Fenestrated
- Sinusoidal
What are some characteristics of continuous capillaries?
No interruptions (pores) in walls
What joins continuous caps together?
Fasciae occludentes
What are some characteristics of fenestrated caps?
Pores (covered by thin diaphragm)
-Can be in clusters
What are some characteristics of sinusoidal caps?
Larger diameter
- Irregular shaped blood pools or channels
- Basal lamina is discontinuous
- Fenestrated but without diaphragms
What are the 3 segments of arteriovenous anastomoses?
- Arterial segment
- Intermediate segment
- Venous segment
Which segment is innervated by adrenergic and cholinergic nerve fibers?
Intermediate
When the shunt is open in arteriovenous anastomoses what happens? Closed?
Blood largely bypasses cap bed
-Closed then blood enters cap bed
What is the purpose of AV anastomoses?
Thermoregulation
-Shunt open when cold to preserve heat
What is the thoroughfare channel?
Distal part of central channel
What do leukocytes bind to on the endothelium to being diapedesis?
Selectins (P, E and L) activation independent (cells still rolling)
- Integrins activation dependent
- Others
What are some characteristics of veins?
Outnumber arteries
- Lumen diameter larger
- Holds 70% of blood
- Parallel arteries and nerves
- Walls collapse due to thinness
- Same 3 layers
What do venules and small veins looks like under section?
Like sinusoidal caps
Where doe leukocytes preferred to emigrate?
Through venules and small veins
What increases and replaces pericytes as venules get larger?
Smooth muscle
-Much material exchanged between vascular compartment and extravascular compartment
What are HEV’s and their function?
High endothelial venules
- Specialized versions of small venules found in some lymphatic organs
- Cuboidal endothelial rather than squamous
- Allow migration of leukocytes
What are the characteristics of medium veins?
- Tunica intima: endothelium; basal lamina; some reticular fibers
- Tunica media: smooth muscle cells intermingled with collagen fibers and fibroblasts
- Tunica adventitia: thickest layer; collagen and elastic fibers
What are the large veins?
Venae cavae Pulmonary Portal Renal Internal jug Iliac Azygous veins
What are the characteristics of large veins?
- Tunica intima: endothelium and a thick subendothelial layer with elastic fibers
- Tunica media: not well developed–often not apparent
- Tunica adventitia: collagen fibers; abundant elastic fibers; vasa vasorum; longitudinally disposed smooth muscle bundles (e.g., inferior vena cava)
What is the arrangement of SM in large veins?
Longitudinal rather than circumferential
What are varicose veins?
Enlarged and tortuous veins
Usually affect superficial veins in legs of older plp
What is the cause of varicose veins?
Loss of muscle tone
- Wall degeneration
- Valvular incompetence
What are some other locations of varicose veins
Lower esophagus
-Terminus of anal canal (hemorrhoids)
What makes up valves?
Folds of intima
-CT rich in elastic fibers
What are lymph capillaries?
-larger diameter than blood capillaries; end blindly in tissue spaces; flimsy basal lamina; endothelial cells held together by a few tight junctions
What are collecting vessels of the lymphatic system?
Vein like structure but thinner walls and valves more closely spaced
What are the main trunks of the lymph vascular system?
Thoracic and right lymphatic ducts have bein like structure
