Download - Vascular Histology
-
8/13/2019 Vascular Histology
1/5
Vascular includes both blood and lymphatic systems.
Arteries are efferent vessels (going away) which become smaller as they branch and carry blood to the
tissues.Capillaries are the smallest blood vessels which serve as the interchange between blood and tissues
Veins are afferent vessels which become larger as they approach and return blood to the heart
Veins
Venule --> medium sized vein --> large vein
Arteries
Arteriole --> muscular artery --> elastic artery
Heart
Internal endocardium
Middle myocardium (cardiac muscle)
External epicardium
On a microscopic level, the heart consists of three layers (tunics):
Endocardium
The first layer (in contact with the lumen). There is a thin layer of endothelial cells. These are supported
by connective tissue with both elastin and collagen (strength).
Connecting the endocardial CT to the myocardial tissue is the subendocardial layer which contains veins,
nerves and perkinje fibres
MyocardiumIt is the thickest layer of the heart and is also known as cardiac muscle. It is comprised of cardiac muscle
cells arranged in layers. In between the muscle fibres there are both a rich supply of capillaries and also
delicate supporting connective tissue.
Vascular
Histology
Striations
Centrally located nucleus (single nuclei)
Branching
Intercalated discs (squiggly line): highly specialised attachment
which joins cardiac cells together and allows them to contract
rapidly as a single unit
Vascular HistologyWednesday, 28 March 2012
3:06 PM
Case Based Learning Page 1
-
8/13/2019 Vascular Histology
2/5
Connective Tissue
Epicardium
The heart is covered externally by a simple squamous epithelium (mesothelium, secretes pericardialfluid) which is supported by CT known as epicardium. The 'epicardium' is also the visceral layer of the
epicardium.
Pericardium
It encloses the heart and holds it in place: outer fibrous and inter serous pericardium
The outer fibrous pericardium is a dense irregular CT which protects and anchors the heart, enabling it
to beat effectively (prevents overstretching). The serous pericardium consists of a parietal (outer) layer,
pericardial cavity with pericardial fluid and a visceral layer (epicardium).
Tissues of the Vascular Wall
Maintenance of selectively permeability barrier
Maintenance of nonthrombogenic barrier (prevents clotting)
Modulation of blood flow
Regulation and modulation of immune responses (enables white blood cells to migrate out
of the blood vessel)
Hormonal synthesis & other metabolic activities
Modification of lipoproteins
Simple squamous endothelium
Involuntary control
Smooth muscle
Larger blood vessels have 3 basic structural components:
Case Based Learning Page 2
-
8/13/2019 Vascular Histology
3/5
Occurs in walls of all vessels larger than capillaries
Arranged helically in layers (wrapped around in concentric layers)
Components vary based on local environments (dependant on function)
Connective tissue
Intima
Has a subendothilial layer with loose CT and a few smooth muscle cells. Has holes to enable substances
to nourish cells in vessel
Media
Concentric layers of smooth muscle cells interspersed with elastic fibres. Arteries
Adventitia
Vaso Vasorum
They are vessels within the walls of vessels which allow perfusion of blood to the cells of the vessel.
More in veins than arteries because veins carry deoxygenated blood. Supply adventitia and outer media.
Elastic Arteries
Large diameter vessels with very thick walls. Generally found closer to the heart (high pressure). Insteadof having large amounts of smooth muscle cells the media is high in elastin content (concentric elastic
laminae). It is able to stretch during systole and recoil during diastole, reduces the fluctuations in BP.
Many vaso varosum in adventitia
Tunica intima, epithelium and CT; lining of BV
Tunica media; smooth muscle; varies diameter of BV lumen (blood pressure)
Tunica Adventitia; Dence CT; tough protective outer coating of BV
Case Based Learning Page 3
-
8/13/2019 Vascular Histology
4/5
-
8/13/2019 Vascular Histology
5/5
Venules
Contain endothelial cells with basement membrane and also a few
smooth muscle cells
As the diameter of the venule increases, the amount of smooth
muscle increases
They drain the capillary network.
Small Veins
The smooth muscle cells form a more continuous layer and eventually a adventitia composed of
collagenous CT is developed.
Intima is a thin endothelium with little CT
Media has less muscle cells (than arteries) and if patchy in arrangement
No internal of external elastic laminae
Adventitia is the predominant layer
Larger Veins