CVS Histology Flashcards
what is the i) conducting system ii) fibrous skeleton of the heart?
– Fibrous skeleton: four fibrous rings surrounding the valves, 2 fibrous triangular structures connecting the rings and membranous parts of the two septa.
– Conducting system: formed by modified muscle cells (Purkinje fibres). Responsible for initiation and propagation of rhythmic contractions.
what are the three layers that make up the heart wall?
Endocardium: This is the inner endothelium lining and its supporting highly elastic fibro-collagenous tissue allowing stretch and preventing damage to the lining epithelium during heart movement.
Myocardium: Comprised of cardiac myocytes, interlinked with intercalated discs with gap junctions on them. These myocytes are supported by fibro-collagenous tissue with extensive vascularisation
Epicardium: The outer fibro-collagenous layer of tissue with large amounts of adipose tissue that carries coronary arteries and autonomic nerves supplying the heart with an outer mesothelium (visceral pericardium) . single layer of mesothelial cells and underlying CT / adipose. BV found here
what does the endocardium specifically consist of? (4)
- single layer of endothelial cells
- subendothelial CT
- middle layer of CT and smooth muscle cells
- deeper layer of CT (subendocardial cells)
what are the arrows, arrowheads, A & B?
describe myocardium layer (4)
- cardiac muscle of the heart (thicker in ventricles)
- layer of interconnected myocytes with associated vessels
- intercalated discs as dense eosinophilic lines
- myocyte fascicles orientated in varying dircections
ONLY FOUND IN THE HEART
what are the arrows pointing to?
Intercalated discs
what are the three layers that make up the heart valves?
– Fibrosa: forms the core of the valve -DIC.
– Spongiosa: LCT on atrial side (loose collagen/elastic fibres), as shock absorber. has bubble morphology (looks like a sponge)
– Ventricularis: Adjacent to ventricular surface of the valve. DCT with elastic fibres. Forms the _chordae tendineae (_fibrous cords covered with endothelium).
(on picture - first arrow: Fibrosa, middle, spongiosa, last - ventricularis)
label the different layers of the heart valves
explain how the cardiac conducting system works x
which are the specifc cells that make up this system?
where does it occur (2)?
- specialised myocytes
- contraction is synchronised by specialised conducting cells
- *location**
i) found in sub-endocardial layer: Purkinje Fibres (convey signals 4x faster thatn muscle fibres - larger & less densely stained)
ii) SA & AV node (smaller)
big arrow in picture points towards: Bundle of His
what type of cardiac cells are these? how can u tell (4)?
purkinjie fibres
- are larger than cardiac muscle fibres
- have central pale staining with most of the common red staining shown in the periphery of the cell. - no T-Tubule system and
- connect with each other via desmosomes and gap junctions rather than intercalated discs.
what are the cells that make up BV?
Tunica Intima:
-The inner-most layers
-All vessels are lined by endothelium
functions:
i) Regulates transport of substances from the lumen into the vessel wall
ii) Controls local clotting through secretion of soluble factors
iii) Enables migration of white blood cells through expression of adhesion molecules
(Some will also be surrounded by a layer of loose connective tissue, and most exteriorly an internal elastic lamina (basement membrane) which separates this tunica intima layer from the tunica media. This lamina is a well-defined sheet of elastin. Fenestrations in this lamina allow for diffusion of substances through the sheet)
- *Tunica Media: The middle layer**
- Contains circularly arranged smooth muscle which contracts to regulate blood flow
- Supporting extracellular matrix with collagen and elastic fibres
- Elastic fibres making up the external elastic lamina separate the tunica media from the tunica adventitia
- *Tunica Adventitia: The outermost layer**
- Loose connective tissue
- Larger vessels of the vasa vasorum: these are the nutrient arteries and veins providing a blood supply to the outer walls of the larger blood vessels.
describe cell structure of vascular endothelium
endothelium: simple squamous epithelium
The endothelium is a thin membrane that lines the inside of the heart and blood vessels
what are the functions of the endothelium?
- Maintenance of a selective permeability barrier, and of non-thrombogenic, barrier-antigoagulants. -Modulate blood flow
- Regulation of the immune system
- Hormonal synthesis and modification of lipoproteins
what are the three different types of artery?
- Large arteries or elastic arteries- aorta and pulmonary arteries.
• Medium arteries or muscular arteries- sometimes difficult to distinguish from elastic arteries.
• Small arteries and arterioles- Can be distinguished from the layers of smooth muscle cells in the tunica media.
what are the three tunica layers like in large / elastic arteries?
compared to medium arteries?
elastic / large arteries
- *Tunica intima** is thick and consists of endothelium, subendothelial CT and an internal elastic membrane.
- *Tunica media** is the thickest with multiple layers of smooth muscle cells (SMC) separated by elastic lamellae. Fibroblasts are not present. SMCs synthesize ECM.
- *Tunica adventitia** is relatively thin, with collagen and elastic fibres, fibroblasts, macrophages, blood vessels and nerves.
medium / muscular arteries:
- *Tunica intima** is thinner with a prominent internal elastic membrane (thickness varies with age).
- *Tunica media** composed entirely of SMC with little elastic material.
- *Tunica adventitia** is relatively thick and often separated from the tunica media by a recognizable external elastic membrane.
which one of these is elastic / muscular artery? how can u tell?
on elastic artery: mostly can see the wavy elastic fibres in tunica media
on muscular artery, much less elastic and can see nuclei of SMC
how many layers of SMC layers are there in the small arterioles / small arteries?
function ?
one or two (arrows point to them)
control blood flow to the capillaries by contraction of SMC
which one of these is the artery / vein?
describe structure of capillaries
what are the three types and where do u find them?
- single layer of endothelial cells and their basal lamina
- contain pericytes (In the CNS, they are important for blood vessel formation, maintenance of the blood–brain barrier, regulation of immune cell entry to the central nervous system (CNS) and control of brain blood flow)
- allow gas and metabolite exchange
3 types
- continous capillary: muscle, lung & CNS
- fenestrated capillary: (with windows) - cytoplasm has pores. endocrine glands, gallbladder, kindey , intestinal tracts
- discontinous capillary: discontinous basal lamina, more molecules pass through: liver, spleen and bone marrow (where get growth of cells)
which type of capillary of each of these? and where each found?
what are the different types of veins (4)
Large veins- Superior and inferior vena cava and hepatic portal vein (> 10mm) •
Medium Veins
Small Veins- Less than 1mm in diameter.
Venules- Subclassified as postcapillary and muscular venules.
thicker tunica adventitia compared to arteries. is the thickest on all three.
which other important structure, apart from ECM, is found in tunica adventitia?
longitudinally disposed SMCs
what are the two types of venules?
how do u distinguish them?
- Postcapillary venules collect blood from the capillary network and are characterized of pericytes (contractible cells wrapped around the endothelial cells). Made up of endothelial, basal lamina and pericytes.
- Muscular venules can be distinguished by the presence of tunica media. Distal to the postcapillary venules and have one to two SMC layers.
(picture on right = postcapil, on left; muscular venules)
which out 1-4 are arteries or veins?
1-3: vein
4: artery
label each type of vein and artery x
how can u distinguish between lympahtic vessels and other types of BV?
The smallest are lymphatic capillaries (converge into larger lymphatic vessels)
More permeable than blood capillaries.
Tubes of endothelium with lack of continuous basal lamina – Numerous in loose connective membrane.
look very thin / non shaped
unidirectional
label the artery, lymphatic and vein
what type of BV (specific) is this?
medium sized vein
what does arrow point to?
what is ^ made from?
valves
These are semilunar projections of tunica intima into the lumen of the vessel. As such they are flaps, or pockets (usually 2 per valve), composed of fibro-elastic tissue covered by endothelium.
what are leaflets on a valve?
EACH VALVE USUALLY CONSISTS OF 2 POCKETS/LEAFLETS. THE FREE EDGES PROJECT IN THE DIRECTION OF BLOOD FLOW, SO PREVENT THE BACKFLOW OF BLOOD
L – LEAFLETS. THE TWO LEAFLETS CAN BE SEEN
what type of capillary is this?
where found?
what is rare with these types of capillary?
fenestrated capillary
location: These are typically found at sites of extensive molecular exchange with the blood, such as the kidney (renal glomeruli are fenestrated capillaries), intestine and endocrine glands
Pericytes are rarely found in association with fenestrated capillaries
what type of capillary is this?
what is P?
continous capillary
The capillary endothelium is supported by a basement membrane (BM) and adjacent collagen fibres. A pericyte (P) embraces the capillary and is supported by its own basement membrane (BMp)
what type of capillary is this?
where found?
Discontinuous capillaries
- The endothelium does not form a continuous lining, i.e. there are gaps between adjacent endothelial cells.
- The basement membrane is either incomplete or absent, and the endothelial cells are usually supported by a fine network of reticular fibres
- These are only found in the liver, spleen and bone marrow where blood components interact directly with the cells in the organ
what type of capillary is this?
fenestrated capillary
label A-E of coronary artery
what are A & B?
