I wasn't sure what to blog about next, so I wrote down all of the fields that we're studying (microbiology, anatomy, physiology, etc.) and let a random number generator pick for me. It picked the number corresponding to Anatomy, so I guess that's what I'll be blogging about now! (Also, I bombed a large proportion of the anatomy questions in the set of formative renal questions that we were given, so I guess I need the extra study...)
Describe the position and functional anatomy of the kidneys and ureters.
The kidneys are located in the abdomen, roughly between T12 and L3. The right kidney is slightly lower than the left kidney because it has been pushed down by the liver. The hilum of each kidney (where the blood vessels etc. join the kidney) is located at around L1-L2. Each kidney is surrounded by a layer of perirenal (or perinephric) fat, which is surrounded by a layer of renal fascia (a.k.a. Gerota's fascia), and then by a layer of pararenal (paranephric) fat.
Demonstrate the topographical relationships of the kidneys and ureters to other
abdominal structures.
The kidneys are located laterally to the psoas muscle, and the ureters run along the front of the psoas. As the ureters enter the pelvis, they cross the bifurcation of the iliac arteries.
Describe the blood supply and innervation of the kidneys and ureters.
Blood supply
The kidneys receive blood from the renal arteries. Since both renal arteries arise from the aorta, and the aorta is on the left side of the body, the left renal artery is shorter than the right renal artery. The opposite is true for renal veins: the left renal vein is longer than the right renal vein. The left renal vein also receives blood from the gonads and adrenals (via the left gonadal vein and the left suprarenal vein respectively).
The ureters receive their blood supply from whatever structures are running close to them. The upper part of the ureters tend to receive blood from the renal artery, the middle part of the ureters tend to receive blood from the gonadal arteries and/or the aorta, and the lower part of the ureters tend to receive blood from the vesical arteries.
Innervation
The kidneys receive sympathetic innervation from T10 and T11 nerves (a.k.a. the lesser splanchnic nerves) and parasympathetic innervation from the vagus nerve. Sensory fibres follow the sympathetic fibres back to T10/T11, so kidney pain tends to be felt over those dermatomes. One important point is that nerves are not very important for renal function in general, but for renal blood flow. Aspects of renal function (how much salt and water to absorb, for example) tend to be controlled by hormones.
The ureters receive sympathetic innervation from T12 and L1, and parasympathetic innervation from the vagus and hypogastric (from S234) nerves. Just like with the kidneys, the sensory fibres follow the sympathetic fibres, so pain in the ureters is felt over T12 and L1.
Describe histology (microscopic anatomy) of the renal cortex and medulla including
the renal corpuscle, proximal convoluted tubule, Loop of Henle, distal convoluted
tubules, and juxtaglomerular apparatus and collecting tubules.
The outer region of the kidney is called the cortex, and is where the renal corpuscles and convoluted tubules are located. (Don't worry, I'll describe what they are and what they do in a bit.) The area deep to the cortex is the medulla, and contains the Loops of Henle and collecting tubules. There is, however, a bit of overlap between these two areas: the columns of the renal medulla contain the structures of the renal cortex, and the medullary rays of the cortex contain structures of the renal medulla.
Renal corpuscle
The renal corpuscle is made out of the glomerulus (a "knot" made out of arteries) and Bowman's space (the first part of the tubular system where urine is formed). Under the microscope, renal corpuscles basically look like a cluster of cells surrounded by a white ring (the Bowman's capsule). The renal corpuscle is the main site where filtration occurs (i.e. the blood gets filtered so that pretty much everything, except for large proteins, is pushed into the Bowman's capsule and the tubular system).
Proximal convoluted tubule
The proximal convoluted tubule is the first lot of tubules. The reabsorption of pretty much all glucose and amino acids occurs here, along with reabsorption of many other substances. Proximal convoluted cells are tall, columnar, and have a brush border to increase their surface area for reabsorption. Since the Na+/K+ pump is critically important for maintaining concentration gradients for reabsorption, proximal convoluted tubule cells have plenty of mitochondria to keep them topped up and ready to go.
Loop of Henle
The loops of Henle have two parts: a thin descending limb and a thick descending limb. The thin descending limb is more permeable to water than salt, whereas the ascending limb is impermeable to water but permeable to salt. The appearance of the Loops of Henle depends on whether you have a cross-section or a longitudinal section of the loop: cross-sections look like little circles, whereas the longitudinal sections look like long white stripes that are lined by cells. (I think. Histology isn't my strong point.)
Distal convoluted tubules and collecting duct
The distal convoluted tubule and collecting duct cells are similar to those of the proximal convoluted tubule, except that cells in the distal convoluted tubule and collecting duct tend to be cuboidal and less metabolically active than those in the proximal convoluted tubule. Both the distal convoluted tubule and the collecting duct are under hormonal control to change the amount of salts and/or water reabsorbed.
Another point of interest is the juxtaglomerular apparatus. The juxtaglomerular apparatus of the distal tubule interacts with the afferent arteriole by secreting hormones etc. to maintain filtration rate (see here).
Describe the histology of the ureter.
Ureters, like many other bodily tubes, have a mucosa, muscularis layers, and an adventitia. (However, unlike many other bodily tubes, they likely do not have a submucosa.) There are two muscularis layers: one is circular, and one is longitudinal. Together, the muscularis layers work to propel urine towards the bladder.
Describe the anatomy of the urinary bladder, its base and ureteric openings and its relationship to the overlying peritoneum.
The bladder is shaped kind of like an upside-down triangular pyramid. The urethra connects to the bladder at the inferior "point." The umbilical ligament, which is a remnant of an embryonic structure called the urachus, joins at the apex, which is the anterior superior "point." The ureters join at the posterolateral points and continue to pass through the wall of the bladder.
One point of interest is the bladder trigone, which is formed from the intermediate mesoderm of the urogenital septum. This is in contrast to the rest of the bladder, which is formed from the anterior part of an embryonic structure called the cloaca. The bladder trigone makes up part of the posterior wall of the bladder. The ureters open into the bladder at the upper lateral corners of the bladder trigone.
Describe the blood supply and innervation of the urinary bladder.
The bladder receives its blood supply from the superior and inferior vesical arteries. The superior vesical artery comes from the patent part of the umbilical artery, which in turn comes from the anterior division of the internal iliac artery. The inferior vesical artery comes directly from the internal iliac artery.
Like the ureters, the bladder receives sympathetic stimulation from T12 and L1. However, its parasympathetic innervation is only from the hypogastric plexus (S234). Both sympathetic and parasympathetic nerves activate muscles, but they activate different muscles: sympathetic stimulation causes the external urethral sphincter to tighten (and stop you from peeing), while parasympathetic stimulation causes the detrusor muscle (i.e. the bladder muscle) to contract, thus making you pee. Sensory information is a bit mixed: pain fibres follow the sympathetic nerves back to T12 and L1, whereas stretch fibres follow the parasympathetic nerves back to S234.
An important reflex to discuss here is the micturition reflex. When the bladder wall is stretched, this information is conveyed back to S234, triggering reflex contraction of the detrusor muscle. When this happens, we feel the urge to pee. However, we can override this reflex through various centres in our brain and through contracting the external urethral sphincter.
Discuss the anatomical reasoning behind differences in referred pain from upper and lower urinary tract infections.
As mentioned, different parts of the urinary tract convey sensory fibres to different parts of the spinal cord. In the kidney, sensory fibres go back to T10/T11, in the ureter they go back to T12/L1, and in the bladder the fibres detecting pain (not stretch) go back to T12/L1. When we feel pain in the urinary tract, we tend to feel it over the dermatomes associated with those sensory nerves: e.g. pain in the kidney is felt over the T10/T11 dermatomes. (However, to my understanding, bladder stones might be felt lower down, like in the S1/S2 dermatomes.)
Describe the anatomy of the urethra; explain the anatomy of its different parts in males and females in relation to continence and catheterisation.
The male urethra is quite long and is divided into three parts (prostatic, intermediate / membranous, and spongy), whereas the female urethra is relatively short and isn't divided into parts. (Some textbooks may consider the pre-prostatic, or intramural, part of the urethra to be a fourth part of the urethra.) Because the female urethra is much shorter, it is easier to catheterise than the male urethra. However, the female urethra is more prone to urinary tract infections than the male urethra. Furthermore, women are more prone to incontinence (though this is also partly because they do crazy stuff like give birth).
An important structure within the male urethra is the verumontanum, also known as the seminal colliculus. The verumontanum is a thickening within the prostatic urethra. It has three orifices: one called the prostatic utricle, and two for the openings of the ejaculatory ducts. The verumontanum is an important marker to look for when removing the prostate via the urethra.
Describe the skeletal and ligamentous components of the pelvis.
Discuss the sexual differences in pelvic skeletal anatomy.
Describe the anatomy and functional importance of the pelvic diaphragm.
Describe the topographical arrangement of anatomical structures within the pelvis.
The pelvis wasn't exactly covered in any of the lectures that we just had (despite pelvic stuff being in the learning outcomes), so I guess it's 2nd year undergrad me to the rescue!
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