Histology of circulatory system Flashcards
What two systems does the circulatory system involve?
The cardiovascular system The lymphatic vaacular system
What is the cardiovascular system made up of?
Closed system consisting of heart, arteries, capillaries and veins
Roles of the circulatory system?
-Transport of nutrients and oxygen to the tissues -Transport of CO2 and other metabolic waste from the tissues - Temperature regulation - Distribution of hormones and immune cells - Reproductive function in males- penile erection
Basic 3 layer structure to a blood vessel?
Tunica Intima - most inner Tunica Media Tunica adventitia
Description of tunica intima?
Single layer of squamous epithelial cells termed endothelial cells, supported by a basal lamina and a thin layer of connective tissue- It is the inner most layer
Description of tunica media?
Made up predominantly of smooth muscle Thickness of this layer varies tremendously
Description of tunica adventitia?
Made up of supporting connective tissue- outer most layer
What is the tunica intima separated from the tunica media by?
Layer of elastic tissue called the internal elastic membrane
What is the tunica adventitia separated from the tunica media by?
Layer of elastic tissue called th eexternal elastic membrane
What colour do elastic fibres stain?
Black
What are the very largest arteries called? And why are they termed this?
Elastic arteries. Because they have many sheets of elastic fibres in their tunica media to provide elastic recoil
Describe the make up of arterioles?
Have only one or 2 layers of smooth msucle in the tunica media and almost no adventitia. They are particularly important in controlling blood flow in tissue.
What are capillaries essentially composed of?
Endothelial cells and a basal lamina
What do capillaries have at intervals just outsude of the basal lamina?
Pericytes - connective tissue cells that have contractile properties
Wher are continuous capillaries found?
In muscle, connective tissue, lung, skin & nerves
Where are fenestrated capillaries found?
Mucosa of the gut, endocrine glands and glomeruli of the kidney
Where are discontinuous capillaries found?
Liver spleen and bone marrow
Description of discontinuous capillaries?
Large gaps through which macromolecules can fit , in some cases even cells can fit through aswell
Basal lamina is discontinuous or not present
What is microvasculature?
Small arterioles connecting to postcapillary venule through this network of metarterioles, thoroughfare channels and capillaries.
What helps control flood flow through microvasculature?
Pre-capillary sphinctors - composed of smooth muscle at the beginning of the capillary
What do capillary networks drain into?
Post capillary venules
Describe post capillary venules?
Endothelial lined and contain a thiin layer of connective tissue and occasional pericytes - important sites for exchange
When is a post capillary venule described as a venule?
When smooth muscle cells start to be acquired in the tunica media layer.
Describe veins?
Thin tunica media- few layers of smooth muscle - markedly thinner than in an artery
Large veins have- thick tunica adventitia - with bundles of longitudnally orientated smooth muscle
Veins are flexible- can accommodate expansion
Have a tunica intima
Difference between large veins and small/medium veins?
Large veins (HPC/VC) have bundles of longitudnally orientated smooth muscle cells
Small/medium veins have Valves- inwards extensions of the tunica intima
What of these is a small artery and which is a small vein?
A= small artery
B = Small vein
3 Layers of the heart?
Endocardium - inner layer
Myocardium - Middle layer
Epicardium- Outer layer
Layers of e heart from the outside in?
Adipose tissue
Fibrous pericardium
} Pericardium
Parietal layer of serous pericardium
Pericardial cavity
Visceral layer of serous pericardium
Epicardium
Myocardium
Endocardium
What does the endocardium do?
Lines the entire inner surface of the heart including the valves
Structure of endocardium?
Endothelium
Basal lamina
Thin layer of collagen fibers
Layer of denser connective tissue
In some areas there can also be a subendocardium of loose connective tissue containing small blood vessels and nerves and branches of impulse conducting system
What is the myocardium?
Thick Middle layer
Structure of myocardium?
Bundles and layers of contractile cardiac muscle fibers
Individual muscle fibers are surrounded by delicate, collagenous connective tissue with a rich network of capillaries
Describe cardiac muscle cells?
Single central nucleus (sometimes 2)
Intercalated discs passing across fibers at irregular intervals
Role of intercalated discs in cardiac muscle cells?
Acts to attach cells but also allows spread of electrical activity
What is the epicardium?
Outer layer of the heart
Structure of epicardium?
Outer layer of heart= Single layer of flattened epithelium called mesothelium
Basal lamina
Fibroelastic connective tissue and in some places adipose tissue
Structure of pericardium?
2 parts
Fibrous pericardium - sac of tough fibrocollagenous connective tissue
Serous pericardium- Layer of simple squamous epithelium, backed by basal lamina and connective tissue
These layers are separated by a thin pericardial cavity containing small amount of pericardial fluid that provides lubrication for heart movement
What does the serous pericardium line?
Inner surface of fibrous pericardium (where is is the parietal serous pericardium)
And also covers the surface of the heart (where it is known as visceral serous pericardium)
What is the hearts fibrous skeleton formed from?
Thick bands of fibrous connective tissue around the heart valves, between atria and between ventricles
This CT supports the valves but also provdes attachmnet for cardiac muscle fibers
Structure of heart valves?
They have
- an outer endothelial layer
- Layers of collagen and elastic fibers
- Core of dense connective tissue (lamina fibrosa) in continuity with fibrous skeleton
- Leaflets of valves separating atria from ventricles are anchored to papllary muscle in walls of ventricles by chordae tendonae
- No blood vessels in valves
-
3 types of cardiac muscle cell?
Contractile cells (99%)
Pacemaker cells
Conducting cells
Describe pacemaker cells?
Highly specialized muscle cells
Considerably smaller than contractile cardiac myocytes
Embedded in extensive matrix of connective tissue
Appear pale
Few myofibrils
Role of the non-conducting tssue of the fibrous skeleton of the heart?
Electrically isolating atria from ventricles
Structure of purkinje fibers?
Larger than normal cardiac muscle cells
Found in subendocardial layer just deep into the endocardium
They have- abudant glycogen, no T-Tubules, no intercalated discs and no sparse actin and myosin filaments
Appear pale
Role of purkinje fibers?
Distribute the excitatory activity such that ventricular contraction generally occurs from inferior to superior
What does the lymph vascular system consist of?
Lymphatic vessels that drain tissue fluid eventually returning it o veins in the base of neck
Describe the role of lymph vascular system?
System of relatively thin walled vessels that drain XS interstitial fluid into blood stream
Most of the XS interstitial fluid returns to capillaries and venous vessels but a portion returns to circulatory system by entering lymphatic vessels
What is in Lymph?
Ions
Lipids
Proteins
Ocassional cells
What makes up for lymoh vessels lack of a central pump?
Smooth muscle iin walls
Hydrostatic pressure in the tissue
Compression of the vessels by voluntary muscle
Combined with valves in the vessels
