Session 1 Anatomy Flashcards
Describe the Anatomical Position of the Kidneys
- Kidneys: retroperitoneal, T12-L3 (right underneath the diaphragm –therefore mobile ~3cm – inspiration, respiration)
- Retroperitoneal – behind the peritoneum – therefore feel pain in the back
- At T11/T12 (right kidney is slightly lower because liver is pushing it down)
- Each weighs about 150g
- 12cm long x 6cm wide x 3cm thick
- Each kidney has single ureter to bladder in the pelvis – smooth muscle tube
- Renal arteries come off at intervertebral discs L1/L2
Describe the anatomical position of the bladder
•lies subperitoneallly in the anterior pelvis, behind the the pubic symphysis and pubic bones
- The bladder sits above the pubic bone in a child.
- It distends upwards when it fills with urine
Describe the anatomical position of the prostate
Sits directly below the bladder. The urethra passes through it and if the prostate undergoes hypertrophy it can prevent urination.
Describe the course of the ureters and the relationships in the pelvis to the iliac vessels and uterine vessels, ovary/vas, and the urethra in both males and females
The ureters arise from the hilum on renal pelvis on the medial aspect of each kidney,before descending towards the bladder on the front of the psoas major muscle (moving laterally to medially). The ureters cross the pelvic brim at level of sacro-iliac joint, anterior to the bifurcation of the common iliac arteries (cross anteriorly over the common iliac arteries)• They then descend the lateral pelvic walls and in the vicnity of the ischial spines they turn medially towards the urinary bladder and enter the posterior surface of the bladder (vesico-ureteric junction) and run obliquely through bladder wall
•In males: pass under ductus deferens and uterine artery, superior to seminal vesicles
•In women: distend posterior to ovary and into base of broad ligament, passing under uterine artery
•Ureter is supplied by branches of common and internal iliac arteries and uterine artery (inferior vesicle artery in males) and drained by veins with the same names.
Bony Landmarks for Course of Ureters
- Arise at ~level of L2
- Descend in front of tips of Lumbar spine transverse processes
- Cross into pelvic brim roughly in front of the sacroiliac joint
- Enter the bladder (Vesico-ureteric junction) at the level of the Ischial spines
Describe the Anatomical Relations of the Kidneys
The T11 and T12 ribs protect the kidneys
•Anterior: to the right kidney – liver, second part of the duodenum and the colon; to the left kidney – stomach, pancreas, spleen, jejunum and descending colon
•Posterior: diaphragm, quadratus lumborum, psoas, 12th rib and three nerves (subcostal, iliohypogastic and ilioinguinal)
•Medial: hilum (deep fissure containing the renal vessels, nerves, lymphatics and the renal pelvis) ; to left kidney – aorta; to right kidney – inferior vena cava
•Superior: adrenal gland
Describe the epithelium in the urinary system
- Renal calices, renal pelvis, ureters, bladder and proximal urethra are lined by transitional epithelium – ability to expand and distend
- The proximal urethra in both sexes is lined with transitional epithelium when then gives way to pseudostratified columnar and stratified squamous epithelium as the urethra opens to the exterior
- In both sexes urethral glands open into the lumen and lubricate the urethral mucosa
Describe the male Urethra
•Long (~20cm), starts at the neck of the bladder and runs through the prostate gland, the floor of the pelvis, perineal membrane to penis and external urethral orifice at the tip of the glans orifice
•Divided into 3 parts
-Prostatic urethra: proximal portion that runs through the prostate gland – transitional epithelium
-Membranous urethra: short middle portion that is enveloped by the external urethral sphincter – pseudostratified columnar epithelium
-Spongy (penile, cavernous) urethra: courses through the bulb of the penis, the pendulous portion of the penis and the glans penis to open at the external urethral orifice – lined by pseudostratified columnar epithelium except for the external opening which is lined by stratified squamous epithelium
• Innervated by the prostatic plexus and lymphatic drainage is to the internal iliac and deep inguinal nodes
•+ a pre-prostatic region that lies between the bladder and the prostate
Describe the female Urethra
- Short (3-5cm)
- Encircled by the urethral sphincter (blends with another skeletal muscle called the sphincter urethrovaginais) and opens into the vestibule
- Starts at the neck of the bladder and passes through the floor of the pelvis and perineal membrane to open into the vestibule just anterior to the vagina – 2.5cm behidn clitoris
- Lymphatics drain to the internal and external iliac lymph nodes.
- Proximally it is lined by transitional epithelium and the rest by stratified squamous epithelium
- Greater risk of UTIs
Describe the structure of a kidney
- Each kidney is enclosed in a tough fibrous capsule and when viewed inferiorly, contains a cortex (outer layer) and medulla
- Nephrons are located in the outer cortex and in a juxta-medullary region, or the deepest part of the cortex
- The tubules of the cortical neurons extend only a short distance into the medulla, whereas the tubules of the juxtamedullary nephrons extend deep within the medulla
- The renal medulla is characterized by the presence of 8 to 15 pyramids (collections of tubules) which taper down at their apex to form the papilla, where the urine drips into a minor calyx.
- Striations are collecting ducts from each nephron
- Several minor calices form a major calyx, and several major calices empty into a single renal pelvis and the proximal ureter
- Calices ‘Collecting cups’
Describe the bladder
- Bladder is enveloped with smooth muscle that is randomly mixed in its orientation and is known as the detrusor ‘drive away’ muscle
- Can hold up to 800-1000ml of urine
- When empty has base (posterior surface)
- The interior posteroinferior wall (base when empty) of the bladder demonstrates a smooth area called the trigone (triangular shape), defined by the two ureteric openings superiorly and the single urethral opening on the inferolateral surface
- Ridge between two urethral openings is interureteric fold
- Neck of bladder is where base and inferolateral sides meet, inferiorly
- Anterior angle or apex, is sight of attachment of urachus – fibrous remnant of fetal allantois, which is seen as medial umbilical ligament on anterior abdominal wall
- In region of neck, detrusor muscle runs circularly as involuntary internal sphincter
- Bladder mucus is thrown into rugae except within trigone
- Opnings are oblique flap valves, closing on bladder contraction
- Prostate is underneath the bladder, in front of the urethral opening
When are the ureters vulnerable?
- Vulnerable: middle 1/3 during abdo surgery and pelvic surgery when close to reproductive vessels
- During hysterectomy, need to be careful you do not clamp the ureters (when trying to clamp arteries to limit bleeding)
Describe the prostate
- Lies below the bladder and surrounding the proximal part of the urethra (prostatic urethra)
- Conical in shape
- Connected to the bladder by connective tissue stroma and has three parts: left lateral lobe, right lateral lobe and middle lobe
- Supplied by the inferior vesical artery and blood drains via the prostatic plexus to the vesical plexus and internal iliac vein
- Lymphatics drain to the internal iliac and sacral nodes
Explain about the internal and external urethral sphincters
- Internal urethral sphincter is not under voluntary control and thus contracts reflexively
- The external urethral sphincter is under voluntary control
- Reflex of urine from the bladder back into the ureter is prevented by a valvular mechanism at the vesicoureteric junction.
- If the valve is incompetent, urinary reflux occurs and chronic pyelonephritis (continuing pyogenic – inflammation and fibrosis – infection) can ensue.
Explain about Micturition (Voidation / Urination)
- Sympathetic nerve fibers relax the bladder wall, allowing for distension and constrict the internal urethral sphincter (smooth muscle) located at the neck of the bladder Micturition is initiated by the stimulation of stretch receptors in the detrusor muscle, sending afferent signals to the spinal cord levels S2-S4 via the pelvic splanchnic nerves
- Parasympathetic efferents (via pelvic splanchnics) induce a reflex contraction of the detrusor muscle, relaxation of the internal sphincter in males and enhance the urge to void pee.
- When convenient (and sometimes not!), somatic efferents via the pudendal nerve (S2-S4) cause voluntary relaxation of the external urethral sphincter (both sexes) and voiding occurs.
- When empty, the external sphincter contracts (in males the bulbospongiosus muscle expels that last few drops of urine from the urethra) and relaxes the detrusor muscle once again under sympathetic control
- The internal uretrhal sphincter may exist in males to prevent reflux of semen into the bladder
Describe the renal blood supply
Each kidney is supplied by a large renal artery which then divides into the follow branches:
•Segmental arteries: one artery for each of about 5 segments
•Interlobar arteries: several arise from each segmental artery and course between the renal pyramids, ascending into the cortex and arching over the base of each pyramid
•Acuate arteries: the arching terminal portions of the interlobal arteries at the base of each renal pyramid
•Interlobular arteries: arise from the arcuate arteries and ascend into the renal cortex
•Afferent arterioles: arise from the interlobular arteries and pass (one each) to the nephron’s glomerulus to form the glomerular capillary network. They come together to form the efferent arterioles.
•Efferent arterioles: glomerular capillaries of the juxtamedullary nephrons reunite to form efferent arterioles that descend into the medulla and form the vasa recta countercurrent system and the peritublar capillary network (maintains an osmotic gradient for tubular function). They eventually drain blood
-In the outer 2/3rds of the cortex the efferent arterioles form a network of peritubular capillaries that supple is all cortical parts of the nephron
-In the inner third of the cortex, the efferent arterioles follow a hairpin course to form a capillary network surrounding the loops of Henle and the collecting ducts down into the medulla. These vessels are known as the vasa recta.
- Supernumerary renal arteries (two or more arteries to a single kidney) are the most common vascular anomaly, occurrency ranging from 25% to 40% of kidneys.
Label this diagram
- Spleen is anterior to the superior pole of the left kidney
- Pancreas points up to the centre of kidney
- Stomach and duodenum sits anterior to the pancreas
- Duodenum wraps around the head of the pancreas
- Most anterior structure is the large intestine
