Lecture 31 Flashcards
What does the urinary system act to do?
The urinary system acts to maintain water and chemical balance in the body by expelling excess water, salts, the wastes of metabolism and many toxins and drugs. It does this via the filtering of blood (about a litre per minute) through the kidneys. The kidneys also act to maintain blood pressure via renin and red blood cell production via erythropoietin.
What does the urinary system need to do its job?
The urinary system needs a delivery system for the blood, a selective filtraation system, a filtrate recovery mechanism and a system to return the recovered, filtered flud to the body. It also needs protection externally and internally, ability to communicate with relevant parts of the body and needs to be adaptable to the body’s changing needs.
What do the kidneys structure allow for and where are they found?
The kidney structure allows blood to be brought into close proximity with the nephron for filtering, a pathway for urine to be removed from the kidney, to be stored and then excreted as well as protection. The kidneys are just below the eleventh and twelth rib (right almost fully below), they are at roughly the T12-L3 vertebrae with the convex side facing laterally, on the medial surface there is a concave notch called the hilum which contains renal blood vessels, lymphatics, nerves and the ureter. They are on the posterior abdominal wall, covered anteriorly by peritoneum (retroperitoneal), they are surrounded, supported and protected by fat.
What parts make up the urinary system?
We have two kidneys (right is slightly lower than the left due to liver pushing down), two ureters which flow from them to the single urinary bladder and then a urethra. It also has many regulatory nerves and muscles.
What is the gross structure of the kidneys?
The kidney has three regions, the cortex (outer, a continuous layer with renal columns(area between medullary pyramids)), medulla (made up of medullary pyramids, each of which ends in a papilla which urine can flow into) and pelvis (innermost). It has a fibrous capsule on the outside. A lobe is a single medullary pyramid and all cortex which surrounds it, the amount of these can be variable, nephrons are packed into these which run down the medulla which give striations). The urine drains from each papilla into calyx, these calayces join to form the renal pelvis, thi then narros as it exits to become the ureter.
What is the path of urine?
The flow of urine is papilla into minor calyx into major calyx into renal pelvis into ureter.
What is the blood path for the kidney?
The blood supply comes off the abdominal aorta into the renal artery, they divide into 5 segmental arteries upon entering the hilum, these brance to form the lobar arteries, which form the interlobar arteries the arcuate ateries (arch over the medullary pyramids) and then interlobular arteries which penetrate the corex, the veins leave via a similar pathway. (There is no direct supply to the medulla and hence it is not important for filtration). Blood supply into the cotex is interlobular artery intoo afferent arteriole into glomerular capillary, away from the cortex is the glomerular capillary, then efferent arteriole and then into peritubular capillaries.
What is the nervous innervation of the kidneys and why is it important.
Innervation is via autonomic nerves and ganglia called the renal plexus, it is supplied by symapthetic nerve fibres from the aplanchinc and other neves, they adjust the diamter of renal arterioles and hence alter blood flow to change filtration amount.
What are the nephrons? What do they do and what is their basic structure?
The nephron is a microscopic functional unit of the kidney, they are the bulk of the kidney and the act to filter blood through selective reabsorbtion and secretion to produce urine. The first part is the bowmans capsule, it is where blood is met and here we find flat cells, once filtered it enters the prosimal convuleted tubule, these cells have big surface area and secretion ability. Next is the loop of henly which goes to the medulla, then the distal convuleted tubule which is for fine tuning and has relatively small size. The prosimal convoluted tubule, loop of henle and distal convoluted tubule are known collectively as the renal tubules. These then empti into collecting ducts which empty into the papilla.
