9. Histology of the Cardiovascular system Flashcards
What are the 3 layers of the heart wall?
What are the 3 layers of a blood vessel wall?
Descrobe the features of the layers (tunica) of the vessel wall?
1 - Tunica intima
- Endothelium (simple squamous)
- Basal lamina
- Subendothelial CT
- Internal elastic lamina (fenestrated for movement of nutrients from lumen into inner BV layer).
2 - Tunica media = SM layer with collagen fibres & elastin, external elastic lamina.
3 -Tunica adventitia
- Fibroelastic tissue (collagen & elastin)
- Vasa vasorum in large vessels (150um - thicker than diffusion distance from lumen)
- Nervi vascularis (nerves of vessels).
Describe the histology of the 3 layers of the heart wall.
What are myocardial cells? Histology?
Myocardial Cells
- Single, striated muscle cells with myofibrils (overlapped actin & myosin myofilaments).
- Linked by intercalated discs = specialized stepped cell junctions.
- Composed of desmosomes (macula adherens), fascia adherens & gap junctions.
- Gap junctions: chemical communication for synchronised contraction.
- Usually single central nucleus, some cells binucleate; clear perinuclear region.
What are Purkinje Fibres?
Histological structure?
Purkinjie Fibres
- Modified cardiac muscle cells involved in conduction of the contractile impulse.
- 4* faster than cardiac myocytes.
- Large, irregular, big & round nucleus, fewer myofibrils (located in periphery) large amounts of glycogen (pale, homogenous).
What is the histology of the cardiac valves?
3 layers?
Heart Valves
- Fibrous rings of the fibrous skeleton of the heart made of dense irregular connective tissue.
- All the valves are fibrous extensions of the rings covered by continuation of the endocardium.
- 3 Layers:
- Spongiosa
- Fibrosa
- Ventricularis
In a table summarise the key histological features and functions of the different blood vessels: arteries, arterioles, capillaries, veins and venules.
What is the nerve supply to all vessels?
Exception?
Do veins or arteries have a larger diameter?
All vessels except capillaries have an autonomic nerve supply.
Veins have larger diameter than paired artery due to bigger return volume.
How can you distinguish an artery from a vein in histological cross section?
What are Pericytes?
Function?
Pericytes = undifferentiated, fibroblast-like cells
- Long branching processes that surround vessels to give support & stability.
- Contractile filaments to control BV diameter & regulate BF.
- Communicate with endothelial cells via gap junctions.
What are the 3 types of capillaries?
- Where are they each found?
- What are the macrophages of the liver sinusoids called? What space do they cover?
What are each of these capillaries?
What is the histology of lymphatic capillaries and vessels?
- Capillary function? Vessel function?
- What does the thoracic duct drain? into what?
- What does the right lymphatic trunk drain? Into what?
Lymphatic capillaries & vessels
- Capillary fn: collect excess ECF & wandering lymphocytes
- Vessel fn: lymph flow.
- Structure:
- Blind-ended tubes, similar to veins (more valves), muscle movement drives flow.
- Endothelium with incomplete BM, capillaries have no media & thin collagen layer (adventitia), larger vessels have muscle bundles & more CT.
- Thoracic duct drains most lymphatic vessels → drains into LSCV at jn of LIJV.
- Right lymphatic trunk drains RUQ lymphatic vessels → drains into RSCV at jn of RIJV.
Summary Table
