Vascular pt 5 Flashcards
How do arterioles regulate capillaries?
Regulate blood flow and which capillaries are perfused. (metarterioles branch from arterioles into capillaries; precapillary sphincters help control flow)
What do capillaries exchange?
Gas and nutrients
What is pinocytosis?
Non-specific fluid and small protein ingestion (preformed by all cells)
Pinocytotic vesicles transport fluid and protein the endothelial cells
What is exocytosis?
Vesicles are released into surrounding tissue
Describe continuous capillaries
Tight, intercellular clefts; contain tight junctions that form major pathway for water and small molecules in skin, muscles, lungs, CT
Describe fenestrated capillaries
Pinocytotic vesicles and channels; thin diaphragms in walls permitting larger molecule passage
Fenestrations are endothelial membrane gaps filled in by a single membrane permitting large molecule passage
Describe discontinuous capillaries
(sinusoid) Intercellular clefts between cells; larger fenestrations permit free passage of proteins and red blood cells
- spleen, liver, marrow
What is capillary action?
Filtration: water and small molecules diffuse out of proximal capillary via hydrostatic pressure
Absorption: water and small molecules diffuse back into the distal side
What are Starling Forces?
Determinations of water and molecular flow among capillaries
Dependent upon: filtration coefficient, capillary reflection, and capillary/interstitial hydrostatic/oncotic pressures
What is the difference between osmotic and oncotic pressure?
Osmotic: pressure exerted by ions across cell membranes
Oncottic: pressure exerted by proteins across epithelium
What is the Net Filtration Pressure (NFP)?
Flow directed out because capillary hydrostatic pressure exceed oncotic pressure
What is Net Absorption Pressure (NAP)?
Flow directed into the capillary because oncotic pressure exceeds hydrostatic pressure
Where do you see a drop in hydrostatic pressure?
Along the length of the capillary (drops below oncotic pressure)
What is interstitial fluid?
What does it contain
- Fluid extravasated from capillaries filling interstitium
- Contains: collagen fiber bundles, proteoglycans, and rivulets of free fluid
How is capillary growth stimulated?
Oxygen depletion–> activation of hypoxia-inducible factor 1 (HIF-1)–>stimulates transcription of VEGF–> diffuses to endothelial cells and activates angiogenesis
What are the four steps of angiogenesis?
- proteases digest local basement membrane
- endothelial cells migrate thru basal lamina to signal source
- endothelial cells proliferate
- cells from tubes and differentiate
What is lymph?
The excess interstitial fluid (10%), small molecules and proteins recovered by lymphatic capillaries
Where are lymphatic capillaries located?
What do they do?
What are flap valves?
What are anchoring filaments?
- Located adjacent to vasc. capillaries
- Terminals absorb excess fluid via interstitial hydrostatic pressure through gaps in lymphatic endothelial cells
- Prevent back flow of lymph
- Prevent collapse in increased interstatial pressure
How is lymph transported?
Where does lymph ultimately drain to?
- SM propels lymph thru valves (response to transmural pressure); sympathetic activity does propulsion; transported thru nodes
- drains into veinous system
What is a lymph node?
- Bean-shaped gland surrounded by dense CT capsule (hilum)
Within a lymph node, what is the purpose of:
- reticular cells
- macrophages
- dendritic cells
- follicular cells
- essentially fibroblasts
- endocytosis
- detect antigens and activate lymphocytes
- antigen-antibody complexes that do long term immune memory
What are lymph nodules?
What are germinal centers?
localized lymphocytes in cortex that form primary and secondary nodules
activated lymphocytes within secondary nodules
What are lymphocytes?
Where do they develop?
What do they do?
- chief constituents of lymph tissue
- bone marrow and lymph tissue
- respond to antigens presented by other cells and generate immune response (enter from HEV and exit thru veins or into sinuses)
Where are the superficial lymphs distributed?
they follow veins and converge onto nodes (widespread); concentrated in the axillary, cervical and inguinal regions
