Anatomy of the CV system 2 Flashcards
What are the components of the CV system?
- Heart
- Arteries
- Capillaries
- Veins
What is the main function of the heart?
Pump
What is the main function of the arteries?
Distribution from the heart
What is the main function of the capillaries?
Main exchange site for nutrients, gases
What is the main function of the veins?
Collect and return to heart
What are the 3 layers of the heart?
- Endocardium
- Myocardium
- Ectoderm
What is the endocardium composed of?
- Epithelium
- Basement membrane
- Connective tissue
What is the myocardium composed of?
Cardiac muscle
What is the epicardium composed of?
- Connective tissue
- Basement membrane
- Epithelium
What are the 3 layers found in blood vessels?
- Tunica intima
- Tunica media
- Tunica adventitia
What is the tunica intima composed of?
- Simple squamous epithelium
- Basement membrane
- Connective tissue
What is the tunica media composed of?
- Smooth muscle tissue
- Elastic tissue
What is the tunica adventitia composed of?
-Fibrous connective tissue
What generalisations can be made about arteries?
- Arteries are smaller in diameter than their accompanying vein
- Arteries have thicker walls than their accompanying vein
How does the thickness of the tunica adventitia and media differ between arteries and veins?
- Arteries have a thick media, thin adventitia
- Veins have a thin media, thick adventitia
How does diameter vary across blood vessels?
Arteries > arterioles > capillaries
How does the total cross-sectional area vary across blood vessels?
Arteries< arterioles< capillaries
What are the 3 types of artery?
- Elastic
- Muscular
- Arterioles
Describe elastic arteries.
Large conducting
Give 3 examples of elastic arteries.
- Aorta
- Common carotid
- Pulmonary
Describe muscular arteries.
Distributing arteries
Give 3 examples of muscular arteries.
- Coronary arteries
- Radial
- Femoral
What are arterioles?
Terminal branches which supply blood to capillary bed
What happens to elastic arteries during systole?
Stretched
What do elastic arteries act as?
Pressure reservoirs
What happens to elastic arteries during diastole?
- During diastole the heart relaxes which leads to a fall in pressure.
- The artery recoils thereby maintaining pressure on the blood
What is the recoil and stretchability of elastic arteries due to?
The presence of extensive amounts of elastic fibres in T. media in the form of layers called laminae
What secretes elastic fibres?
Smooth muscle
What do muscular arteries do?
Control distribution of blood to regions
What does the thick T. media of muscular arteries contain?
Smooth muscle cells
What cannot be found between the muscle cells in the T. media of muscular arteries?
Elastic lamina
How are elastic fibres arranged in muscular arteries?
-Elastic fibres are concentrated in 2 well defined sheets call the internal elastic lamina (IEL) just under the epithelium and the thin outer elastic lamina (OEL) between T media and T adventitia
What happens to the smaller muscular arteries?
The gradually change histologically to become arterioles
What is lacking in arterioles?
- IEL
- T adventitia
What are arterioles composed of?
- Endothelium
- Basement membrane
How many layers of smooth muscle are there in the T media of arterioles?
1-2 layers
What do arterioles control?
- Local: control blood flow to capillary beds
- Systemic: control blood pressure
What is lacking in capillaries?
- T media
- T adventitia
What are capillaries composed of?
- Endothelium
- Basement membrane
What are pericytes?
Incomplete layer of cells surrounding basement membrane. They have contractile properties which help control flow of blood in the capillaries
Why is blood pressure in the capillaries low?
The sum of diameters of all capillaries in the body> diameter of the aorta
What property of capillaries make them suited to their function?
Thin walled
What is the only layer that capillaries have?
T intima
What are the 3 types of capillaries?
- Continuous
- Fenestrated
- Discontinuous
What are continuous capillaries responsible for?
Selective transport mechanisms
Where are continuous capillaries found?
Muscle
What can continuous capillaries control?
Can control what is exchanged
How does material pass through continuous capillaries?
Material must pass trough cells or between cells (junctions can control)
How are fenestrated capillaries characterised?
- Have fenestrations (or pores)
- With or without protein diaphragms
What do protein diaphragms do in fenestrated capillaries?
Filter molecules by MW &/or charge
Where are fenestrated capillaries found?
- Endocrine glands
- Kidney renal corpuscle
How are discontinuous capillaries characterised.
Contain gaps between endothelial cells (and basement membrane)
What do the gaps in discontinuous capillaries allow?
Free passage of fluid and cells
Where are discontinuous capillaries found?
- Liver
- Spleen
- Bone marrow
What are sinusoids?
Large diameter discontinuous capillaries
Where are sinusoids found?
Where large amounts of exchange takes place:
- Liver
- Some endocrine glands
What does the T intima of sinusoids contain?
Phagocytic cells
What do arteriovenous shunts do?
Bypass capillary beds
When do AV shunts occur?
Skin in thermoregulation
What are the blood vessels involved in the venous system?
- Capillary bed
- Small venule
- Small/medium sized vein
- Large vein
What is the structure of veins?
- T intima is thin
- IEL and OEL thin or absent
- T media is very thin or absent
- T adventitia - collagenous tissue
- Valves
What is the purpose of valves in the venous system?
To prevent back flow
How to valves present in veins?
As endothelial projections into the lumen
Where is the difference between superficial and deep veins most obvious?
Lower limb
Describe superficial veins.
- Thick walled
- No surrounding support
Describe deep veins.
- Thin walled
- Surrounding support from deep fascia and muscles
Where are deep veins usually found?
-Deep veins lie next to their corresponding artery and are often found near the bone
What is the fate of superficial veins?
Ultimately drain into deep veins
What does the lymphatic system do?
Drains tissue fluid lost from blood capillaries
What happens after fluid travels through the lymphatic system?
It drains into the systemic venous system
Where are lymph nodes found?
Nodes found alongside major veins and around origins of major arteries
What do valves in the lymphatic system do?
Direct flow
What is the lymphatic system clinically important in?
Tumour cell metastases
What are lymph capillaries lined by?
Very thin endothelium
What kind of capillaries are lymph capillaries?
Blind ended
What is absent in lymph capillaries?
- Fenestrations
- Absent/ rudimentary basal lamina
- RBC
What pressure maintains the lumen of lymph capillaries?
Negative hydrostatic pressure
What is the role of anchoring filaments in lymph capillaries?
Fine collagenous filaments link endothelial cell to surrounding tissue keeping lumen open
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