Blood vessels and lymphatics Flashcards
What is the tunica intima
Innermost layer, creates the lumen - endothelium
What is the tunica media
Smooth muscle and elastin fibres - vasoconstriction/dilation
What is the tunica externa
Outermost layer of connective tissue - collagen fibres protect and reinforce the vessel and anchor to surrounding structures
What is the structure of tunica intima
Lined with simple squamous epithelium called the endothelium
What is the structure of tunica media
Concentric layers of smooth muscle with varying amounts of elastic fibres. Contains the sympathetic vasomotor nerve fibres
What is the structure of tunica externa
Sheath of longitudinally oriented connective tissue – primarily collagen fibres and elastin. Contains vasa vasorum
What is vasa vasorum
Network of small blood vessels in the largest vessels (i.e. aorta, brachiocephalic and coronary arteries). Branch profusely in the externa and outer part of the media
What is the function of the vasa vasorum
It nourishes the outer layers and responds to nutrient needs
What is the structure of muscular arteries
They have the thickest tunica media layer. They have more smooth muscle and less elastic tissue than elastic arteries
What is the function of muscular arteries
They are more active in vasoconstriction. They accomodate an increase in diameter and can contract to prevent haemorrhage
What is the function of arterial anastomosis
Hand as an example: ensure supply to the hand and fingers in any position of the upper limb. All joint have anastomoses around them
What is the structure of arterioles
They are the smallest of the arteries. The smaller arterioles have only a single layer of smooth muscle and endothelium but the larger ones have all 3 layers
What is the metarteriole
It is the capillary bed end of arteriole
What are pre-capillary junctions
Sphincters control blood flow within the tissues
What is vasomotion
In response to neural, hormonal and chemical influences blood flow is shunted to maintain blood pressure to vital organs
What are capillaries
They are endothelial cells supported on a basal lamina. They form a network called a capillary bed
What are the 3 types of capillaries
Continuos, fenestrated and sinusoid
What are continuous capillaries
They are most common. They have associated pericytes. They are the least permeable
What are fenestrated capillaries
They have large pores for active filtration
What are sinusoid capillaries
They are the fewest of them. They are the most permeable. Blood flows slowly. They facilitate passage of large molecules and cells
What are venules
They are the smallest veins. They are extremely porous. Venules unite to form veins
Describe the ways of venous return
- Veins can be associated with arteries - artery pulsation aids movement of blood within veins
- Muscle contraction can propel blood along
- Respiratory pump - thoracic and abdomen pressure changes as a result of breathing aid blood return
What is the azygous system
It drains the venous blood of the posterior thoracic wall to SVC
What is the hepatic portal vein
Venous blood from the components of the GI tract, as well as the spleen, does not return directly to the heart. Instead it forms the hepatic portal vein, which takes the venous blood through the liver before it then joins the IVC
What is the function of the lymphatic system
It collects interstitial fluid lost from the vascular capillary beds and returns it to systemic circulation
What is the function of lymph nodes
They filter lymph and are usually clustered at specific sites
What are superficial and deep lymph nodes associated with
Veins and arteries
Where do smaller/superficial lymph vessels drain into
They drain into larger/deep vessels before returning to the venous sytem
What is the downfall of the lymphatic system
It can spread infection. For example, tumour cell migration from original tissues can seed in nodes
