Tissues + Structures - Blood vessels and Lymphatics Flashcards
Do vessels have different origination?
Yes.
What is a feature of vessels in embryology?
Some vessels supplying an organ can migrate far from its origination.
What happens in the gonad vessels?
These vessels may elongate to reach the organ.
What happens with the kidney vessels?
New vessels appear, replacing the old ones as the organ migrates.
Where do the vessels supplying the kidney originate from?
The pelvic brim - supplied by the prolongation of the dorsal aorta - median sacral artery.
What is the pathway of the vessels that supply the kidney?
As the kidney goes up the posterior abdominal wall, it is supplied successively from internal and common iliac arteries. Then supplied by series of branches from the abdominal aorta.
What are abnormal renal arteries?
One or more aortic branches.
Are veins bigger than their corresponding arteries?
Yes.
What is the reason that veins are bigger than their corresponding arteries?
Rate of flow in veins is slower.
How does blood flow in veins in the foot and hands?
Via the dorm - to avoid the pressure of the palm and sole, this would construct the veins.
What are venae comitantes?
A pair of veins - normally seen in peripheral limbs.
What happens in proximal limb veins?
The venae comitantes unite into a single large vein e.g. axillary and popliteal.
Why do large veins have big space around them?
To allow for great dilatation during increased blood flow.
Where does the axillary vein lay?
In front of the pre-vertebral and axillary fasciae.
Where does the femoral vein lay?
Alongside the femoral canal.
Describe the internal jugular vein and the carotid sheath?
The carotid sheath sits loosely around the IJV.
Describe the carotid artery and the carotid sheath?
Carotid sheath sits tightly around the artery.
Where do the pulmonary veins lay?
Lower part of the lung root - this is to allow for expansion of the vein between the two lax layers of the pulmonary ligament.
What does the dead space alongside large veins contain?
Regional lymph nodes e.g. deep inguinal nodes alongside the femoral vein.
What are the smallest vessels?
Capillaries.
What do capillaries consist of?
Flattened endothelial cells.
What are the layers of other vessels?
Three layers:
1. Tunica intima (innermost).
2. Tunica media.
3. Tunica adventitia (outermost).
What does the tunica intima consist of?
Endothelial lining with a variable amount of underlying CT.
1. Endolthelium.
2. Basement membrane.
3. Subendothelial CT.
4. Internal elastic membrane.
Describe tunica intima layer in the artery?
Has an internal elastic lamina - this gives a crenated appearance to the lumen of the artery.
What are the types of arteries?
- Elastic.
- Muscular.
- Arterioles.
What does the tunica media consist of?
Circular smooth muscle fibres and there is an external elastic lamina at the junction of the media and adventitia.
Describe the tunica media in large vessels like the aorta and their branches?
They have a large amount of elastic tissue mixed with muscle fibres.
Describe the tunica media in veins?
Thinner.
Describe the tunica intima layer in veins?
There is no internal elastic lamina.
Describe the IVC?
It does not have any tunica media.
What are venous valves?
Valves in many veins that prevent a reversal of blood flow.
Where do you commonly see venous valves?
Lower limb e.g. great saphenous vein has 15 valves.
What do valves consist of?
Two posed cusps.
What veins don’t have valves?
- SVC.
- IVC.
- Veins of head and neck.
- Ophthalmic veins.
- Dural sinuses.
- Vertebral veins.
- Cardiac veins.
- Hepatic veins.
- Pelvic veins.
- Portal veins and its tributaries.
What are the types of anastomoses in arteries?
- Actual.
- Potential.
Describe actual anastomoses?
Arteries meet end to end.
Where do you find actual anastomoses?
- Labial branches of facial arteries.
- Intercostal arteries.
- Uterine and ovarian arteries.
- Arteries of greater and lesser curvatures of the stomach.
- Arterial arcades of the mesentery.
- Marginal artery of the colon.
Describe potential anastomoses?
Anastomoses at the terminal arterioles.
Where do you find potential anastomoses?
- Coronary arteries.
- Limb anastomoses in the regions of joints.
- Cortical arteries of cerebral hemispheres.
What are end arteries?
No pre-capillary anastomosis between adjacent arteries.
What happens if there is interruption of blood flow at end arteries?
Gangrene or infarction.
Where do you find end arteries?
- Liver.
- Spleen.
- Kidney.
- Lung.
- Medullary branches of CNS.
- Retina.
- Straight branches of mesenteric arteries.
What are short circulating channels known as?
Shunts or arteriovenous anastomoses.
What is lymphatic return?
Blood that enters a “part” that doesn’t return via vein, becomes tissue fluid and returns via way of lymphatics.
Where do superficial lymphatics follow?
Classically seen in subcutaneous tissue, these will follow veins.
Where do deep lymphatics follow?
Arteries.
Where does tissue fluid first enter?
Intricate plexus of minute lymphatic vessels (capillaries).
What are the pathways of lymph fluid?
Originally lymph fluid can go anywhere depending on local and distant pressures.
What happens when lymph fluid reaches the lymph valves?
The route of lymph fluid becomes definite.
What is the rule of disease in lymphatics?
Disease such as infection or neoplasm does not follow strict anatomical pathways.
What happens if lymphatics become dilated?
If they are dilated due to obstruction, their valves may be separated and reversal of lymph flow can occur.
What are the defence mechanisms of the body?
- Phagocytosis.
- Immune response.
What is phagocytosis?
Non-specific engulfing process.
What is the immune response?
Specific reaction to micro-organisms and foreign proteins (antigens).
What are the types of immune response?
- Humoral - antibody response.
- Cell-mediated immune response.
What happens in the humoral response?
Antibodies (protein molecule) are produced and attach to foreign protein so that the antigen can be destroyed by phagocytosis.
What happens in the cell-mediated response?
Specific cells circulate the body and either kill the antigen or stimulate phagocytosis.
What cells produce the humoral response?
B-cells.
How do B-cells produce the humoral response?
B-cells become plasma cells, the plasma cells produce antibody molecules (IgG, IgM etc.).
What cells produce the cell mediated response?
T-cells.
Where do lymphocytes come from?
Common stem cells in the bone marrow.
Where do T cells originate from?
Thymus.
What happens to T cells after they are released from the Thymus?
They colonise the spleen, lymph nodes and other follicles. They pass through post-capillary venues of those structures.
What are the type of T cells?
- T helper.
- T suppressor.
- T killer (cytotoxic).
- T memory.
What are the type of B cells?
- Plasma cells.
- B memory cells.
What are the lymphoid organs?
- Thymus.
- Lymph nodes.
- Tonsils.
- Spleen.
What is the characteristic structural feature of lymphoid organs (except the thymus)?
Lymphoid nodule or follicle.
What is the lymphoid nodule/follicle?
Spherical collection of lymphocytes with a pale central area - germinal centre.
Where else do lymphoid follicles occur?
Mucosa and submucosa of all parts of the alimentary and respiratory tracts e.g. Peters patches in the gut.
What is the largest mass of lymphoid tissue in the body?
Gut associated lymphoid tissue (GALT).
How do lymphoid follicles in mucosa work?
M cells (special enterocytes) that overly mucosal lymphoid follicles absorb antigenic material, this is then exposed to intraepithelial and follicular lymhpocytes and macrophages. To allow for an immune response.
How are lymphocytes organised in the thymus?
Continuous dense band of tissue at the outer region or cortex of the lobules.
What are the regions of the lobules in the thymus?
- Inner regions form the medulla.
- Continuous cortex.
What does the medulla in the lobules of the thymus contain?
Thymus corpuscles of Hassall.
are the thymus corpuscles?
Remnants of the epithelium of the third pharyngeal pouch.
Where are rounded follicles of lymphocytes concentrated in a lymph node?
Periphery (cortex).
Where are non-follicle lymphocytes concentrated?
- Paracortical areas.
- Medullary region of the hilum of the node - efferent lymphatic vessels leave.
Where are B lymphocytes found?
- Follicles - proliferate in germinal centres.
- Medulla.
Where are T lymphocytes found?
- Paracortical areas (thymus dependent zone).
- Cortex between the follicles.
What vessels do the lymph nodes receive?
- Afferent lymph vessels.
- Efferent channels - in which they drain.
Describe the lymph tissue in tonsils?
They possess lymphoid follicles (similar to lymph nodes) except tonsils have a covering of stratified squamous epithelium on their inner service, this goes to form the tonsillar crypts.
How is tonsil tissue distinguished from lymph nodes histologically?
Presence of stratified squamous epithelium.
What is the unique identifying feature of the splenic follicles?
Arteriole goes near the germinal centres of the lymphoid follicle inn the spleen.
Where are T cells found in the spleen?
Immediate periarteriolar region of the follicle.
Where are B cells found in the spleen?
Germinal centre.
What do all lymphoid organs contain (except lymphocytes)?
- Phagocytic cells (macrophages, histiocytes).
