Arteries And Veins Flashcards
Types of arteries
Conducting elastic and distributing muscular
Pulmonary circulation
The right side pumps the blood into the capillaries of the lung
Systemic circulation
The left side pumps the blood to the rest of the body
Exceptions of the role arteries and veins
Pulmonary arteries and veins
Umbilical arteries and veins
These in conditions where arteries/high o2 and veins/low o2
Blood supply to the artery
Vasa vasorum
What is the tunica interna or intima
Innermost layer consisting of endothelial cells that is the site of gaseous exchange in capillaries
What is the tunica media?
Smooth muscle cells and elastic net layer, it is the middle layer that varies in content.
- In arteries close to the heart it is mainly elastic to allow for the expansion and relaxation of vessels
- further from the heart the tunica media of peripheral arteries and arterioles = more smooth muscle fibres
What is the tunica externa
Anchors the vessels to the surrounding tissue and contains the vegetative nerves as well as the vasa vasorum
How do capillaries structure and density vary between different tissues and organs they supply?
Sinusoid capillaries in liver and spleen
Structure of venules and veins
The have the same 3 layers, but a larger diameter and much thinner tunica media = adaptation to much lower blood pressure
Adaptation of veins
They have valves formed by the tunica interna which prevents backward blood flow
- contraction of surrounding skeletal muscle and pulsation of adjacent arteries promote venous return
What are venous sinuses
These are veins with no valves or tone in liver and spleens. They can store a huge amount of blood,
What is vasculogenesis?
- No bone marrow in embryos, so blood cells and endothelial cells give rise to the blood vessels
- form in blood islands of the embryonic and extra embryonic mesoderm
What are blood islands?
Small cell clusters where the peripheral cells give rise to the endothelial cells and the central cells become blood cells
They extend and fuse together to make the first vascular networks
What are the sites of vasculogenesis
- extraembryonic = blood islands of the extraembryonic mesoderm in the yolk sac merge to form the capillary network draining into the veins that brings nutrients and gases to embryo
- intraembryonic = forms the dorsal AOTA and posterior cardinal veins that connect to capillary networks born in mesoderm of each organ. Capillary networks or independently within the mesoderm of each organ and connect later to the vessels emerging from the newly formed aorta
What is angiogenesis
- Primary capillary networks are formed and remodelled, veins and arteries are made
- Endothelial cells from existing blood vessels can be recruited to sprout new vessel or migrate to distant sites forming new vessels or capillary networks
- responsive to VEGF or hypoxia
- arteries and veins made from the same endothelial precursor cells
Zebra fish model organism
Separation of arterial and venous cells occurs early
Angioblasts are born in the posterior part of the lateral plate mesoderm and migrate to the midline of the embryo where they combine to form the aorta and cardinal vein beneath it
These angioblasts are already fated to come either artery-making cells or vein making cells
Zebra fish evidence
Artery and vein making cells are separate:
- ephrin b 2
- eph b4
- cell surface receptors
What are angioblasts
A type of endothelial cell precursor derived from bone marrow
Role of cell surface receptors in remodelling of blood vessels
- enquire connections between venous and arterial vessels in the capillary plexus
- ensure fusion fo capillaries to make larger vessels occur between between same type of vessels
Role of vasculogenesis and angiogenesis in adult body
- new blood vessels after injury
- in muscles following exercise
- new vessels (collat circulation) to bypass blocked vessels
Why is VAN in close proximity
- arteries form in response to VEGF > can induce angioblasts in the tissue to form adjacent nerves
- nerves secrete angiogenic factors
- arteries can secrete nerve growth factors
What does peripheral circulation include?
- arteries veins and nerves often grouped together as VAN
- large vessels found superficially (cephalon vein in forelimb and saphenous vein in hind limb)
- arteries can be paired = bilateral symmetry
- almost all collateral arteries join w/other arteries (anastomose) forming a network of blood vessels (rate arteriosum)
- terminal or end arteries
What is the regulation of peripheral circulation
- arteriovenous anastomoses: connection between arterioles and venules bypassing a capillary bed
- barrier arteries and sphincter veins: structures able to interrupt flow to or from capillary bed
- rete metabile: exuberant parallel branching from a blood vessel that reunite a single vessel
- sphincter veins
What composes the portal circulation
- hepatic portal
- hypophyseal portal
- renal portal ( in non mammals )
Hepatic portal circulation
- takes venous blood from gastrointestinal tract, spleen and pancreas to capillary bed in liver
- function: absorption and detox of metabolites before systemic circulation
- hepatic portal vein brings venous blood to the sinusoids of the liver
- hepatic veins draw venous blood from liver into caudal vena cava
