Histology Flashcards
The three layers of blood vessel walls?
Tunica intima
- Endothelium & it’s basal lamina
- Thin layer of sub-endothelial Connective Tissue.
Tunica media
- Circular layers of smooth muscle & elastic CT
Tunica adventitia
- CT with loosely arranged elastic and collagen fibres & scattered smooth muscle cells
Function of endothelial cells?
Selective barrier
Secrete vasodilators and vasoconstrictors
Secrete anticoagulants
Secrete immune modulators e.g. Interleukins
Examples of elastic arteries?
Conducting: Aorta, pulmonary. carotid
Features of elastic arteries? (5)
Large diameter
T. Media is thick
Lots of elastic laminae & smooth muscle cells in between.
T. adventitia is relatively thin
Fibroelastic CT with scattered smooth muscle cells & vasa vasora.
What is vasa vasora?
Vessels with the CT of larger vessels to feed inner smooth muscle.
Examples of Large/collecting Veins?
Vena cavae
Features of Large/collecting veins? (5)
Large, often collapsed
T. media is very thin
Very few layers of elastic laminae & smooth muscle cells
T. adventitia relatively thick
Fibroelastic CT occupying longitudinal bundles of smooth
muscle & vasa vasora
Examples of muscular arteries?
Radial, femoral & splenic
examples of medium veins?
Renal & hepatic
Features of muscular arteries?
Medium diameter
T. Media is Thick
Multiple concentric smooth muscle and fibro-elastic cartilage in between media and adventitia
T. Adventitia is relatively thick
Fibro-elastic CT with scattered smooth
muscle & .Vasa vasora
Internal & external elastic laminae
Features of medium veins?
Medium diameter
T. Media is thin
2-3 concenric smooth muscle layers
T. Adventitia is relatively thick
Fibro-elastic CT with scattered smooth muscle & Vasa vasora
Valves
Differences/similarities in arterioles and venules?
Arterioles have a small lumen and thick wall, venules are the opposite.
Both have thin T. intima
T.Media: Arterioles have 1/2 layers of smooth muscle in fibroelestic CT, venules may have some cells but not layers.
T. adventitia is very thin in both
Arterioles may have internal elastic lamina whereas venules may have valves
What vessels are there in the microcirculation?
The vessels between the arterioles and venules:
- Metarterioles - Terminal arteriole branches, regulate the blood flow through capillaries
- Capillaries, lined by epithelial cells
- Arterio-venous shunts, link arterioles directly to venules, to divert blood away from capillaries.
Three types of capillaries?
Continuous:
- Most common
- Lined by endothelium
- Limited permeability
Fenestrated:
- Located in intestine and kidney mostly
- continuous but have fine trans-endothelial channels
- Highly permeable and allow large molecules through
Discontinuous:
- Found in liver, bone marrow and lymph nodes
- Wide irregular lumens
- Highly permeable to large molecules and even blood cells.
Features of the epicardium?
analogous to T. adventitia
consist of visceral pericardium & fibrous adipose tissue CT beneath
Thickness varies with amount of adipose tissue
Occupies branches of Coronary vessels and nerves
What layer of the vessels is the epicardium analogous to?
Tunica Media
Features of the myocardium?
Thick middle layer
Consists of bundles of Cardiac muscle cells and vascular loose CT
Substantially thicker in the left ventricle
Contents of the endocardium?
Endothelium and sub-endothelial fibroelastic CT covered by endothelium.
Where/what is the fibrous skeleton of the heart?
Dense CT typically in the interventricular septum, and in the atria-ventricular plane and around the valves.
Function of the fibrous skeleton of the heart?
Maintains the integrity of the openings it surrounds
Provides attachment for the valves/cardiac muscles
Electrically isolate the conduction system and the atria from the ventricles.
Functions of the lymphatic system?
Drains excess fluid and lymphocytes back into the systemic circulation?
Regulates interstitial fluid pressure and plasma volume
Removes foreign substances and debris from tissue.
Three main divisions of the lymphatic system?
Lymphatic capillaries
Medium & large lymphatic vessels
Thoracic duct and right lymphatic duct
What are the different parts of the Nephron?
Proximal Convoluted tubule
Descending thick limb
Descending thin limb
Ascending thin limb
Ascending thick limb
Distal Convoluted tubule
Collecting tubules
Collecting ducts
What does the cortex contain?
Renal corpuscles, Proximal Convoluted Tubule, Distal Convoluted tubule.
Collecting tubules and some collecting ducts
Three types of nephrons?
Subcapsular nephrons
Juxtamedullary nephrons
Intermediate nephrons
Histological make-up of the Renal corpuscle?
Bowman’s capsule
Vascular Pole (where blood vessels enter)
Urinary Pole (opens to PCT)
Filtration apparatus
Urinary space
Three filtration barriers of the glomerulus?
- Glomerular endothelial cells
- Glomerular basement membrane
- Podocytes
the layers of the Glomerular basement membrane?
Lamina rarae, on both inner and outer, polyanionic, stops charged molecules
Lamina densa in the middle (thick collagen mesh)
Epithelium of the DCT And PCT?
Simple cuboidal epithelium, Both have brush-border (microvilli) brush border in more abundant in the PCT than the DCT.
The epithelium of the loop of henle?
simple squamous in the thin limbs, simple cuboidal in the thick limbs.
Structure of the juxtaglomerular apparatus, and function?
Macula densa - monitor Na and Cl in the blood, and blood volume
Juxtaglomerular cells secrete renin
Lacis cells - support
What areas of the urinary system are lined by transitional epithelium?
ureter, urinary bladder and urethra.
Structure of the ureter?
Made up of three layers:
- Mucosa with transitional epithelium and the lamina propria
- Muscularis Mucosa (2-3 smooth muscle layers)
- Serosa/adventitia
5 stages of filtration in the nephron?
- Filtration in the glomerulus
- Obligate reabsorption in the PCT
- Generation of osmotic gradient in loop of henle
- Resorption and secretion in the DCT
- Regulation of water content in the collecting duct
How is the filtration pressure of the glomerulus regulated in changing blood pressures?
By constriction or dilation of the afferent arteriole.
In low BP dilation of arteriole and vice versa
