CTO Post Quiz #5 Material Flashcards
What is a meant by a lobe of the kidney?
A kidney LOBE (not lobule) consists of a medullary pyramid, cortex and half of the renal columns on either side.
If you looked at a medullary ray under the microscope, what would be the dominant feature?
A mecullary ray contains collecting tubules.
What does the cortical labyrinth consist of?
The cortical labyrinth consists of renal corpuscles and convoluted tubules.
Follow the course of blood through the kidney from the renal artery to the renal vein.
The renal blood supply goes from the renal artery to the segmental arteries, to the interlobar arteries, to the arcuate arteries, to the interlobular arteries, to the afferent arterioles, to the glomerular capillaries, to the efferent arterioles to the cortical capillary plexus. From here, blood can drain to the interlobular veins or to the vasa rectae. Both the interlobular arteries and the vasa rectae connect into to the arcuate veins, which convey blood to the interlobar veins, which drain into the renal veins.
Where does the capillary plexus in the cortical labyrinth come from?
The capillary plexus around the convoluted tubules arises comes from efferent arterioles.
What is unusual about the embryonic development of the nephron and the collecting ducts?
The components of the nephron and the collecting ducts have different embryonic origins and must connect during embryogenesis.
Which tubules in the cortex are located primarily in between lobules of the kidney?
Collecting ducts are located mostly in the area in between lobules of the cortex.
Where are renal corpuscles located in the cortex?
85% of renal corpuscles are in the upper cortex, while 15% are juxtamedullary.
What is different between the uriniferous tubules of juxtamedullary renal corpuscles?
The juxtamedullary renal corpuscles have longer loops of Henle, extending deeper into the renal medulla.
What is the barrier between the blood and the urinary space (Bowman’s space) in the renal corpuscle?
The barrier consists of fenestrated endothelium, a basement membrane, and podocytes with filtration slits between pedicles.
What is the structure of the visceral layer of Bowman’s membrane? The parietal?
The visceral layer consists of podocytes; the parietal layer consists of simple squamous cells.
What is the function of mesangial cells?
Mesangial cells clean deposited proteins off of the basement membrane of the glomeruli.
What is unusual about the basement membrane of the glomerulus?
The basement membrane has charged proteins and proteoglycans to filter big proteins.
What is the progression of filtrate through the uriniferous tubules?
Filtrate progress through proximal convoluted tubules, thick descending limbs (of Henle), thin descending limb, thin ascending limb, thick ascending limb and the distal convoluted tubule. This ends in a collecting tubule that connects to a collecting duct.
What is the structure of the wall of the distal convoluted tubules?
The DCT consists of simple cuboidal epithelium without a brush border.
On H&E stain, how can you distinguish PCT from DCT?
The cells of the PCT are redder (more eosinophilic) and taller than the cuboidal cells of the DCT. Also the cells of the PCT have microvilli.
What is the structure of proximal convoluted tubules?
The PCT consists of simple cuboidal epithelium with a brush border.
A renal lobule is defined by:
All of the nephrons that drain into a collecting duct.
What is the structure of descending and ascending thin limbs (of Henle)?
They are comprised of simple squamous epithelium.
Why are the thin decending and ascending limbs adjacent to one another?
This allows countercurrent exchange of sodium to prevent dilution of the sodium concentration in the renal medulla.
What is the function of the thick limb of Henle?
It is impermeable to water but pumps sodium to produce a high sodium concentration in the renal medulla.
What is the structure of the collecting ducts?
Collecting ducts are lined by cuboidal epithelium with prominent infoldings of lateral cell borders.
What hormone has the most powerful influence on collecting ducts?
Collecting ducts are affected by anti-diuretic hormone (ADH) that allows water to escape from the collecting duct into the medulla of the kidney, where it is picked up by the vasa rectae.
What are the components of the juxtaglomerular apparatus?
The JGA consists of several compnents. The macula densa, which is a specialization of the DCT that detects Na+ and fluid levels. Juxtaglomerular cells (JG) are modified smooth muscle cells that secrete renin. Extraglomerular mesangial cells have a function that is not well understood.
What do JG cells secrete and how do they affect the body?
JG cells secrete rennin, which converts angiotensinogen to angiotensin I. This, in turn, is converted to angiotensin II by angiotensin converting enzyme. Angiotensin II has effects on blood vessel contraction and on secretion of aldosterone from the adrenal cortex. This hormone, in turn, causes blood volume elevation by fluid retention at the DCT.
What is the pathway for urine from the medullary pyramid outward?
Collecting ducts open onto the renal papilla, which empties urine into the minor calyx, to the major calyx, to the renal pelvis, to the ureter, to the urinary bladder and finally out the urethra.
What is the epithelium that lines the lower urinary tract?
It is transitional epithelium (urothelium), which changes shape (flattens) when the system is distended. These cells have prominent terminal bars.
What are the layers of the ureter?
The mucosa is on a thick lamina propria. It has no submucosa. There is a thick muscularis, but layers are not distinct. There is an adventitia outside.
What is the structure of the urinary bladder?
It has a lining of transitional epithelium on a lamina propria. There is no submucosa but a thick smooth muscle layer. Outside is an adventitia.
What does the immune system do?
The immune system is responsible for the defense of the body against the limitless array of potential pathogens and other foreign material (macromolecules, microorganisms, viruses, transformed cells, etc.) that we encounter on a daily basis.
What are the components of the innate immune system?
The innate (native, natural) immune system is provided by epithelial barriers and their secretions, and by a host of cells (macrophages, granulocytes, natural killer (NK) cells, etc) that can destroy or remove foreign elements by means of non-specific, stereotypical mechanisms.
What is the specific immune system?
The specific (adaptive, acquired) immune system is provided by B-lymphocytes (B-cells) and T lymphocytes (T-cells), which mediate a very specific humoral (antibody-mediated) or cell-mediated immune response respectively. Cooperation between the innate and the specific immune system is the rule, and both humoral and cell-mediated responses may work together in the defense of the organism.
What provides the specificity of the adaptive immune system?
The specificity of the adaptive immune system is provided by immunoglobulins (antibody) or by T-cell receptors (TCRs), each of which has the ability to recognize one of potentially billions of different foreign molecules.
What molecules mark the cell as “self”?
The recognition of ‘self’ is mediated by the human leukocyte antigen (HLA) complex (major histocompatability complex; MHC).
Where would you find MHC I?
MHC I is a receptor molecule that is a transmembrane protein found on virtually all nucleated cells. MHC I displays antigens (normal or abnormal) produced inside those cells.
Where would you find MHC II?
MHC II is a transmembrane receptor found on antigen presenting cells (APCs) that is specifically designed for displaying exogenous foreign antigens and “presenting” them to the lymphocytes.
How do B-cells recognize antigens?
B-cells recognize antigen by means of surface-bound immunoglobulins (Igs).
What are the types of antibodies?
Several types of immunoglobulins (antibodies) exist (IgM, IgD, IgG, IgE, IgA).
What are the fundamental units of all antibodies?
All antibodies share a common basic structure, which includes two heavy chains and two light chains (which come together to form an Fc [constant] region) and an antigen-binding region, the Fab domain.
During maturation, what are the initial antibodies on a B-cell?
IgM and IgD represent the initial B-cell surface immunoglobulins.
What are the first antibodies secreted by a recently formed plasma cell?
The first soluble antibodies secreted by a plasma cell are low affinity IgMs.
What is isotype switching?
Cells resulting from the clonal expansion of the original B-cell will undergo affinity maturation and isotype switching resulting in the secretion of higher affinity antibodies (IgG, IgE or IgA). IgG is the predominant Ig found in blood; IgA is, overall, the most abundantly produced of the Igs and is found in many bodily secretions (saliva, mucous, breast milk); IgE is associated with molecules typically considered allergens.
What provides the specificity of the T-cell response?
The T-cell receptor provides the antigen specificity for the T-cell response.
What are the MHC-I restricted T-cells?
MHC I restricted T-cells are CD8+ cytotoxic lymphocytes (CTLs).
What are the MHC II restricted T-cells?
MHC II-restricted T-cells are CD4+ TH cells.
What is the usual process of a humoral immune response?
A humoral immune response is usually initiated by the binding of antigen to the membrane-bound immunoglobulins on the surface of a B-cell. That antigen will be processed by the B-lymphocyte and then presented in association with MHC II to a TH cell. The release of cytokines by the T-cell will then trigger a clonal expansion of that B-cell into plasma cells and memory B cells.
How are NK cells involved in the humor response?
Antibodies may be used for opsonization of foreign cells and their subsequent destruction by phagocytosis or NK cell-mediated lysis.
How are macrophages involved in the immune response?
Exogenous antigens can be phagocytosed and processed by macrophages (or other APCs), which then present that antigen in the company of MHC II to TH cells. This triggers proliferation of that particular TH cell (to yield additional TH cells including memory cells) as well as the secretion of cytokines to stimulate increased macrophage activity. This may also activate appropriate B-cells, which is why we now recognize the mutual interactions of humoral and cell-mediated immunity.
How are abnormal cells (including those infected by viruses) recognized?
Endogenously produced antigens (e.g. produced by virus-infected cells or tumor cells) will be expressed on the cell surface in association with the MHC I complex. These antigens are recognized by the CD8+ CTLs, which are then activated, resulting in proliferation, memory cell production and cytokine secretion.
How do cytotoxic lymphocytes kill target cells?
Cytotoxic lymphocytes kill target cells by the secretion of lytic agents (e.g. perforins, granzymes).
Inside the capsule of the thymus, what are the portions of the thymic parenchyma?
There is a cortex and a medulla of the thymus.
What makes up the stroma of the thymus?
The epithelioreticular cells (ERC) are the stroma of the thymus. There is no connective tissue within the thymus.
What happens to the thymus in adulthood?
It becomes a fatty, involuted structure in the adult.
What is the function of the thymic cortex?
The thymic cortex has positive selection. Thymocytes that bind strongly to MHC I are selected and allowed to proceed to mature in the medulla. Those that don’t recognize self are signaled to undergo apoptosis.
What is the function of the thymic medulla?
Thymocytes that recognize and react against self MHC I are selected against and triggered to undergo apoptosis. If they are not adequately screen out, these thymocytes may result in autoimmune disease.
What is the function of the epithelial reticular cells?
These are associated with thymocyte differentiation and selection. They secrete a large number of thymic hormones. They provide selection barriers that prevent all but certain cells from entering the thymus. ERC I are the blood-thymic barrier. ERC II express MHC I and II and are the cells that positively select thymocytes. ERC III cells are the barrier between cortex and medulla. ERC IV are on the medullary side of the cortico-medullary junction and ERC V have both MHC I and II and are the negative selecting cells. Finally ERC VI are the cells that make Hassall’s corpuscles.
