CVS Histology Flashcards
What does endocardium and tunica intima consist of?
Endothelium + BM + Connective tissue
What does myocardium and tunica medica consist of?
Muscle + Elastic tissue
What does epicardium and tunica externa consist of?
Fibrous Connective tissue + Epithelium (only epicardium)
Give characteristics of endocardium?
Lines heart chambers
Simple squamous epithelium sitting on basement membrane
Sits on connective tissue
Forms valves
Give characteristics of myocardium?
Thick middle layer of heart wall
Cardiac muscle (Myocytes) – branching fibres
Striated muscle, lots of mitochondria, single central nucleus
Rich capillary bed
Muscle bundles in different planes (spiral) to close down chamber lumen on contraction
Myocytes connected by intercalated discs
Give characteristics of epicardium?
Outer layer of heart wall
Simple squamous epithelium + BM + Connective tissue
Epithelium = visceral layer of serous pericardium
Epicardium contains main branches of coronary arteries
May be fatty
Compare arteries and veins?
Artery:
Thick muscle wall
Smaller, thicker wall
Thin adventitia
Vein:
Thin muscle wall
Larger, thinner wall
Thick adventitia
What are the types of arteries and give examples?
Elastic – large, conducting – eg: aorta, common carotid,
pulmonary
Muscular – distributing arteries – eg: coronary arteries, radial, femoral
Arterioles – terminal branches which supply blood to capillary bed
What is the benefit of elastic arteries for e,g, in aorta?
Pressure reservoir
Stretched during systole
During diastole heart relaxes pressure falls, the artery recoils thereby maintaining pressure on the blood
This recoil and stretchability is due to presence of extensive amounts of elastic fibres in T. Media in the form of many layers/laminae
The elastic fibres are secreted by the smooth muscle cells
Give characteristics of muscular arteries?
Controls distribution of blood to regions
Thick T. media has smooth muscle cells but no elastic laminae
Elastic fibres are concentrated into 2 well-defined layers: the internal elastic lamina (IEL) just under epithelium, and the thin external elastic lamina (OEL) between T. media & T. adventitia (TA)
Give characteristics of arterioles?
The smaller muscular arteries gradually change to become arterioles
Only 1-2 layers of smooth muscle in T. media
No IEL or EEL
No T. adventitia
Rich sympathetic nerve innervation
Control blood flow to capillary beds
Control blood pressure (systemic)
Give characteristics of capillaries?
Main exchange site for nutrients, gases.
Therefore, very thin T. intima
No T. media
No T. adventitia
Pericytes – incomplete layer of cells surrounding capillary - have contractile properties which control blood flow.
Low blood pressure in capillaries
What are the 3 types of capillaries?
continuous
fenestrated
discontinuous/ sinusoids
Describe continuous capillaries?
composed of a single layer of simple squamous epithelium = endothelium, basement membrane, and scattered connective tissue cells called pericytes.
Can control what is exchanged
Material must pass through cell, or between cell (junctions can control)
Selective transport mechanisms
Eg. in muscle
Describe fenestrated capillaries?
Have fenestrations (or pores)
Diaphragms filter molecules by MW &/or charge
Eg. endocrine glands, kidney renal corpuscle
Describe discontinuous/ sinusoids capillaries?
Gaps between endothelial cell and basement membrane
Allow free passage of fluid and cells
Eg. liver, spleen, bone marrow
Give characteristics of sinusoids?
Large diameter type of discontinuous capillaries
Found where large amount of exchange takes place
T. intima contains phagocytic cells
Eg. liver
Describe Arteriovenous (AV) shunts?
bypasses capillary beds
e.g. in skin for thermoregulation
Give characteristics of superficial veins?
Thick walled
No surrounding support
Give characteristics of deep veins?
Thin walled
Surrounding support from deep fascia and muscles
Superficial veins drain into deep veins
DVT (=Deep Vein Thrombosis)
Describe lymphatics?
Drains tissue fluid lost from blood capillaries
Drains into the systemic venous system via L+R subclavian veins
Lymph nodes found alongside major veins and around origins of major arteries
Valves direct flow
Clinically important in tumour cell metastases
Describe lymph capillaries?
Blind-ended capillaries
Lined by very thin endothelium
Anchoring filaments - fine collagenous filaments link endothelial cell to surrounding tissue to keep lumen open
No red blood cells in lumen:
- key to ID a lymphatic channel
from a blood vessel
What do blood vessels themselves receive?
Nerve supply
Sympathetic + parasympathetic
Blood supply
Vasa vasorum
(= “vessels of the vessels”)
Lymphatics
In T. adventitia
