Blood and Lymphatic Vessels Flashcards
What are the three layers that make up the walls of blood vessels?
- tunica interna
- tunica media
- tunica adventitia
Describe the tunica interna
- layer that faces the lumen in a blood vessel
- contains endothelium of SIMPLE SQUAMOUS cells with a basement lamina underneath
- basement lamina is a CT layer
- may or may not have an internal elastic lamina, depending on the vessel
- elastic arteries and muscular arteries do have IEL (pink squiggly looking line)
Describe the tunica media
- middle layer
- variable amount of smooth muscle:
–> elastic arteries have the most smooth muscle; veins have less than elastic arteries
–> medium arteries have fewer muscle layers, arterioles have even fewer, and capillaries do not have any
elastic arteries > large veins > medium arteries >medium veins > arterioles > capillaries - veins and venules always have fewer muscle layers than their artery counterparts
- some vessels, like elastic and muscular arteries, also have External Elastic Lamina (EEL) - interspread with muscle
- collagen is present, not visible
What vessels have external elastic lamina in their tunica media?
elastic and muscular arteries
What vessels have an internal elastic lamina in their tunica intima?
elastic and muscular arteries
Describe the tunica adventitia
- outer CT layer that connects blood vessel to the surrounding tissue
- for larger blood vessels, this layer will contain the blood vessels and nerves that service the outer layers
(because blood supply within vessels won’t reach furthest parts of outer layer if too thick-typically thicker smooth muscle layer)
Describe lymphatic vessels
- very thin
- basal lamina not continuous
- single-ended
- no tight junctions between cells
- fluid leaks in and valves prevent it from moving back up or out
What is the function of vasa vasorum
- supplies blood to (larger) blood vessels
What is the function of nervi vasorum
- supplies nerves to blood vessels
- allows for constriction of smooth muscle
What are the three types of capillaries?
- continuous capillaries
- fenestrated capillaries
- sinusoidal capillaries
Describe the structure/function of continuous capillaries
- maintain tight junctions with each other and do not let any materials leak through
- exchange of materials occurs across the cell membrane via pinocytotic vesicles in a process called transcytosis - controlled exchange
- found in lungs, CNS, CT, and muscle
Describe the structure/function of fenestrated capillaries
- capillaries are filled with holes called fenestrae
- -> this allows for faster exchange between blood and outside world
- found in choroid plexus, gallbladder, intestines, and endocrine glands
Describe the structure/function of sinusoidal capillaries
- large gaps and holes in these capillaries, allowing materials to leak out of capillary
- lumen has a large diameter
- unimpeded access to surrounding tissues
- located in places where a high degree of exchange must occur between the blood and tissue (liver, lymph nodes, adrenal cortex, spleen, and bone marrow)
What is the function of lymphatic vessels?
- they collect fluid that leaks out of capillaries and post-capillary venules and return them to the blood
- lymph vessels are single-ended, have many openings and very thin walls, and have valves to prevent the fluid from flowing back out of the vessel
How does the structure of lymphatic vessels help support their function?
- lymph vessels are single-ended, have many openings and very thin walls, and have valves to prevent the fluid from flowing back out of the vessel
