Anatomy of the CVS 2: histology of blood vessels Flashcards
What are the 3 tunics of blood vessels?
- Tunica intima
- Tunica media
- Tunica externa/adventitia
What are the 3 layers of the heart wall?
- Endocardium
- Myocardium
- Epicardium
What is the tunica intima composed of?
Epithelium + BM + Connective tissue
What is the tunica media composed of?
Muscle + Elastic tissue
What is the tunica externa (adventitia) composed of?
Fibrous connective tissue
- Connective tissue is to anchor the vessel and support it.
Differences between arteries and veins
- Arteries smaller diameter than accompanying vein.
- Arteries thicker wall than accompanying vein.
- Arteries thick media thin adventitia.
- Veins thin media thick adventitia.
What are the diameters of arteries, capillaries and arterioles from biggest to smallest?
Arteries > Arterioles > Capillaries
What are the 3 types of arteries?
- Elastic
- Muscular
- Arterioles
Features of elastic arteries
- Large conducting
e. g. aorta, common carotid, pulmonary.
Features of muscular arteries
- Distributing arteries
e. g. coronary arteries, radial, femoral.
Muscular arteries are essentially conducting the blood towards the organ.
Features of Arterioles
- Terminal branches which supply blood to capillary bed.
Why can’t you see the smooth muscle in Elastic arteries upon miscroscopy?
Because it is covered by elastic fibres in the media.
- The elastic fibres are secreted by smooth muscles.
- Elastic fibres are stretched during systole.
in muscular arteries, which tunic contains smooth muscle cells?
- Thick tunic media has smooth muscle cells.
- No elastic laminae between muscle cells in tunic media.
In muscular arteries, where are the elastic fibres found?
-Elastic fibres are concentrated in 2 well defined sheets called the internal elastic lamina (IEL) just under epithelium, and the thin external elastic lamina (EEL) between T.media & T. adventitia
How are arterioles formed and what do they contain?
- The smaller muscular arteries gradually change histologically to become arterioles.
- No IEL (internal elastic lamina)
- No T.adventitia
However, they have a rich sympathetic nerve innervation.
Features of capillaries
- Main exchange site for nutrients, gases.
- Therefore very thin walled
- T. intima only: endothelium on BM
- No T. media
- No T. adventitia
- Pericytes: incomplete layer of cells surrounding basement membrane – have contractile properties which help control flow of blood in the capillaries.
- Blood pressure in capillaries is LOW.
What are the 3 types of capillaries?
- Continuous
- Fenestrated
- Discontinous
Features of continuous capillary
- Can control what is exchanged
- Material must pass through cell, or between cell(junctions can control)
- Selective transport mechanisms
- Eg. in muscle
Example OsPe question
What kind of capillary is this, and give an example of where you would find this kind of capillary?
Features of Fenestrated capillary
- Have fenestrations (or pores)
- Fenestrations up to 100μm
- With or without protein diaphragms
- Diaphragms filter molecules by MW &/or charge
- Eg. endocrine glands, kidney renal corpuscle
Feautures of discontinuous capillaries
- Gaps between endothelial cells (and basement membrane)
- Allow free passage of fluid and cells
- Eg. liver, spleen, bone marrow
What are Sinusoids and features of them?
- Large diameter discontinuous capillaries
- Found where large amount of exchange takes place
- T. intima contains phagocytic cells
- e.g. liver, some endocrine glands
Do arteriovenous (AV) shunts bypass capillary beds?
Yes
e.g. in skin for thermoregulation
Features of Superficial veins
- Thick walled
- No surrounding support
- Superficial veins will eventually drain blood into the deep veins!!
Features of Deep veins
- Thin walled
- Surrounding support from deep fascia and muscles
- Deep veins have a corresponding artery nearby
Features of the Lymphatic system
- Drains tissue fluid lost from blood capillaries
- Drains into the systemic venous system
- Nodes found alongside major veins and around origins of major arteries
- Valves direct from
What is the lymphatic system clinically important for (bad)?
Tumour cell metastases
Features of Lymph capillaries
- Blind-ended capillaries
- Lined by very thin endothelium
- No fenestrations
- Absent/rudimentary basal lamina
- Lumen maintained at nehative hydrostatic pressure
- Anchoring filaments: fine collagenous filaments link endothelial cell to surrounding tissue keeping lumen open.
- NO red blood cells in lumen
Nerve supply in blood vessels as organs
- Sympathetic e.g. skin
- Sympathetic + parasympathetic e.g. heart
Blood supply in blood vessels as organs
- Thick blood vessels have blood vessels of their own in the adventitia called VASA VASORUM, “vessels of the vessels”
Where as lymphatics in blood vessels found?
In T.adventitia
