Cardiovascular Histology Flashcards
Inner lining of lumen of every blood vessel?
Endothelium (simple squamous epithelium)
Three layers of blood vessels?
- Tunica Intima: Endothelium
- Tunica Media: Smooth muscle
- Tunica Adventitia: connective tissue
What is Endothelium? Functions?
-specialized simple squamous epithelium in blood vessels
Functions:
- semipermeable barrier between blood and interstitial fluid
- mediates and monitors exchange of small molecules
- converts angiotensin 1 to angiotensin 2
- converts biologically active compounds to inert
- lipolysis: triglycerides and cholesterol
- produce vasoactive factors
- antithrombogenic action
What types of vessels do not have a tunica media?
- capillaries
- pericytic venules
How are smooth muscle cells connected in small arteries and arterioles?
gap junctions
Tunica Intima?
- one layer of endothelial cells
- some arteries have internal elastic lamina (large to small)
- IEL have fenestrae to allow diffusion, keep lumen open
Tunica Media?
- concentric layers of smooth muscle
- elastic and reticular fibers
- some arteries have external elastic lamina right before tunica adventitia (medium muscular)
- large arteries have multiple layers of elastic lamina
Tunica Adventitia?
- collagen type 1 and elastic fibers
- Vasa vasorum (vessel of vessel, smaller vessels in adventitia)
Large elastic arteries?
- Aorta and branches
- elastic lamina (tunica media) stabilize blood flow
- many layers of elastic lamina
- Tunica intima is thickest of all arteries
Medium muscular artery?
- Tunica intima has prominent IEL
- Tunica media is made up of about 40 layers or less of smooth muscle
- some have EEL in tunica media
- Tunica adventitia defined
Small Muscular artery?
- Tunica media is about 10 layers of smooth muscle
- Tunica adventitia defined
Arterioles?
- Tunica media is less than 5 layers of smooth muscle
- no IEL
Capillaries?
- no Tunica Media or Adventitia
- only contain Tunica Intima
How to identify a venule?
- runs with arterioles
- has bigger lumen
- always identify the artery next to it
How to identify lymphatic vessel?
- runs with arteries and veins
- usually big open space above or below other vessels
- has endothelium
Carotid bodies?
- chemoreceptors in Common Carotid
- sense high CO2, low O2 tension, acidic pH
- nerves are afferent, send signals to brain
- fenestrated capillaries in cells (rapidly measure and exchange chemicals)
Carotid Sinus?
- Baroreceptors in Internal Carotid
- sense change in blood pressure
- Tunica media thinner, allow to sense more change
- Tunica media and Adventitia rich in nerve endings
- afferent impulses are processed by CNS to control vasoconstriction
Capillaries?
- one or two endothelial cells and basal lamina, contain windows for exchange
- pericytes
- arteriovenous anastomoses: regulate BP, flow, temp
- Exhange vessels: water, O2, small molecules diffuse, large molecules through fenestrae
- usually one or two endothelial cells with RBC in middle
Pericytes?
- a lot of actin/myosin in cytoplasm
- intimately attached to capillary
- stem cells differentiate into new capillaries
- sense pressure through capillary
Different types of capillary structure?
-varying levels of metabolic exchange
- Continuous or Somatic:
- tight junctions (zona occludens)
- ex. pancreas, muscles - Fenestrated or visceral:
- most common
- in all visceral organs
- basal lamina is continuous, but easier movement of cells
- ex. jejunum - Discontinuous or Sinusoidal:
- in liver
- big open areas for blood to purify
- slow flow
- discontinuous basal lamina
Venules?
- irregular, collapsed lumen
- few smooth muscle cells
Small to medium veins?
- thin Tunica Intima
- Tunica media small bundles of individual muscle cells, reticular and elastic fibers
- Tunica adventitia well developed
Large veins?
- venous trunks close to heart
- Tunica intima well developed
- Tunica media few layers of muscle and CT
- Tunica adventitia thick with long bundles of smooth muscle
First vein leaving capillary bed (postcapillary)?
pericytic venule
Lymph vessels?
- single layer of endothelium that originate in tissue as closed ended capillaries
- return extracellular fluid to heart
- incomplete basal lamina
- converge to form Thoracic duct
- similar structure to veins but thinner walls and less distinct tunica
- valves control unidirectional flow of lymph
Where does the thoracic duct drain?
junction of left Internal jugular vein and left subclavian vein
Summary: differences between arteries and veins?
Artery:
- prominent IEL in Intima
- many layers of smooth muscle in Media
- CT in Adventitia
Vein:
- thin sub endothelial layer in Intima
- small bundles of smooth muscle in Media
- well developed and collagenous Adventitia
Layers of heart?
- Endocardium= Tunica Intima
- endothelial layer - Myocardium= Tunica Media
- cardiac muscle, inserts into fibrous skeleton - Epicardium= Tunica Adventitia
- CT, vasa vasorum, adipose
Structure of cardiac valves?
-collagen and elastic fibers lined both sides with endothelium
Sinoatrial node (SA)?
- located in upper right atrium
- natural pacemaker
- 60-100 bpm
Atrioventricular node (AV)?
- located in floor of right atrium
- network of cytoplasmic projections
- conduct normal impulses
Atrioventricular bundle?
- associate with AV node
- Purkinje fibers: impulse conduction system (bigger, binucleate muscular cells, stain foamy color: glycogen)
- signal to innermost layers of ventricular musculature
Atherosclerotic lesions?
- antithrombogenic function of endothelium lost
- aging CT
- obstruction of vessel by atherosclerotic plaque
- thrombosis at location of lesion
Aneurysm?
- localized dilation of arterial wall
- bulging Tunica Media
- if smooth muscle wall breaks it is fatal
