Anatomy - SUGER Flashcards
What is the inguinal canal?
What does it lie superiorly to?
-Oblique passageway through the muscles of the anterior abdominal wall
-Lies superior to the medial half of the inguinal ligament
Through where does the inguinal canal pass?
-Through each layer of the abdominal wall as it travels medially and inferiorly
-Starting at the transversalis fascia deep and laterally
-Finishing with the external oblique aponeurosis superficially and medially
How long is the inguinal canal in adults and from where does it extend to and from?
-5cm long in adults
-Extends from deep inguinal ring (aperature in transversalis fascia) to superficial inguinal ring (aperature in the external oblique aponeurosis)
What do these mark?
Entry and exit of inguinal canal
What do these show?
Inguinal canal
What forms the anterior border of the inguinal canal?
-External oblique aponeurosis
-Laterally only: internal oblique aponeurosis
What forms the posterior border of the inguinal canal?
-Transversalis fascia
-Medially only: medial fibres of the aponeuroses of the internal oblique and transversus abdominis (together called conjoint tendon)
What forms the roof and floor of the inguinal canal?
Roof:
-Transversalis fascia
-Arching fibres of the internal oblique and transversus abdominis
Floor:
-Inguinal ligament - rolled up lower border of the external oblique aponeurosis
What are the contents of the inguinal canal in females?
-Round ligament of uterus
-Ilioinguinal nerve
-Genital branch of the genitofemoral nerve
What is this and what does it form?
-Inguinal ligament
-Floor of the inguinal canal
What do these form?
(arching fibres of internal oblique)
-Form roof of inguinal canal
What are these?
Contents of inguinal canal in females
In males what are all the contents of the inguinal canal contained within?
-Spermatic cord
-EXCEPT for ilioinguinal nerve which runs in the canal but lies outside the spermatic cord
What can the contents of the spermatic cord be divided into?
-Two nerves
-Three arteries
-Three fascial layers
-Four other structures
What are the nerves spermatic cord?
-Gential branch of genitofemoral nerve
-Sympathetic nerve fibres
What are the 3 arteries of the spermatic cord?
-Testicular artery
-Cremastatic artery
-Artery to vas deferens
What are the 3 fascial layers of the spermatic cord and their derivations?
-External spermatic fascia - EO aponeurosis derived
-Cremaster muscle and fascia - IO muscle derived
-Internal spermatic fascia - transversalis fascia derived
What are these?
Three fascial layers of spermatic cord
What are the four other structures in the spermatic cord?
-Pampiniform venous plexus
-Lymphatics
-Vas deferens
-Processus vaginalis
Describe scrotal skin and what is beneath it:
-Thin, wrinkled and more darkly pigmented that elsewhere
-Beneath is a thin layer of superficial fascia and a thin, involuntary muscle called the dartos
What does the superficial fascia of the testes extend to form?
Extends between the testicles to form a septum dividing the scrotum into right and left halves
What does each half of the scrotum contain?
-Testis
-Epididymis
-Lower part of spermatic cord
What is the function of testes?
-Male reproductive organs
-Produce sperm and secrete the sex hormone testosterone
Describe the testes and their coverings:
-Ovoid structures
-Covered by the same three layers of spermatic fascia that cover the spermatic cord
What are the testes partially covered by and what is it derived from?
Partially surrounded by a sac derived from peritoneum called tunica vaginalis
Describe the epididymis:
-Coiled tube lying along posterior border of each testis
-Expanded head superiorly
-Body
-Pointed tail lying at the lower pole of the testis
Describe the formation and movement of spermatozoa in the testes:
-Formed in the testes
-Stored in the epididymis
-Vas deferens carries sperm from the epididymis and travels with the testicular vessels in the spermatic cord
Where do testicular arteries arise?
Direct branches from the abdominal aorta
What is the venous drainage of the testes?
-Venous blood from the testis and epididymis enters the pampiform venous plexus
-Pampiform venous plexus forms testicular vein
-Right testicular vein enters the inferior vena cava
-Left testicular vein joins the left renal vein
What is the penis function?
Male organ of sexual intercourse
What is the penis primarily made up of?
-Three cylinders of erectile tissue
-Two corpus cavernosa dorsally (top of penis)
-One corpus spongiosum ventrally (bottom of penis)
What are the cylinders of the penis and what are they enclosed in?
-Corpus cavernosa and corpus spongiosum
-Enclosed within deep fascia of the penis - Buck’s fascia
Describe the end of the penis:
-Called the glans
-Expansion of the corpus spongiosum
What carries urine and semen and where does it lie in the penis?
-Penile urethra
-Lies within corpus spongiosum
-Approaches end of penis and opens via external urethral meatus
What is the arterial supply of the penis?
-Penile arteries
-Branch from the internal pudendal arteries which branch from the internal iliac arteries
What is the nerve supply to the penis?
-S2-S4 segments
-General sensation + sympathetic innervation = dorsal nerve of penis - branch of pudendal nerve
-Parasympathetic arise from peri-prostatic nerve plexus
What are parasympathetic nerves of the penis responsible for?
Dilating arteries of the corpora
What are primarily responsible for the increase in size and rigidity of the penis during erection?
Corpora cavernosa
What happens to the penis during sexual intercourse?
-Arterial blood flow into the corpora of the penis increases
-Corpora become engorged with bloods
-Spongiosum does not engorge to the same extent as the cavernosa
What is the main role of the corpus spongiosum during erection?
Prevent the urethra from being compressed, which would prevent ejaculation
What two terms are used interchangeably for the adrenal glands?
-Adrenal
-Suprarenal
Where do the adrenal glands lie?
-Close to upper pole of each kidney
-Right - lies behind the liver and inferior vena cava
-Left - lies behind the stomach and pancreas
What arteries supply each adrenal gland?
-3 arteries
-Superior adrenal artery - phrenic artery branch
-Middle adrenal artery - abdo aorta branch
-Inferior adrenal artery - renal artery branch
Label:
What are they?
Blood supply to adrenal glands
What is the venous drainage of the adrenal glands?
-Single vein on either side
-Right adrenal vein - IVC
-Left adrenal vein - drains first into left renal vein which then joins IVC
What is the adrenal gland composed of?
-Cortex (outer part)
-Medulla (inner part)
What do the cortex and medulla of the adrenal glands produce?
-Cortex - steroid hormones including cortisol, aldosterone and testosterone
-Medulla produces adrenaline
Are the kidneys intraperitoneal or retroperitoneal?
-Extra-peritoneal
-Retro-peritoneal as they are behind the peritoneum
Where do the kidneys lie?
-There is one on either side of the upper lumbar vertebrae
What are the layers that the kidney is embedded in?
-Each kidney embedded in perinephric fact
-This fatty layer is covered by renal fascia
-A further layer of paranephric fat is found outside the renal fascia
What is found on the medial border of each kidney?
-Renal hilum
-Renal vessels, nerves, lymphatics and ureter enter or leave the kidney
Where do the renal arteries and veins branch or drain into?
-Both renal arteries are branches of abdominal aorta
-Both renal veins drain into IVC
What makes up the internal aspect of the kidney?
-Cortex - outer part
-Medulla - inner part arranged into pyramids
-Calyces
Which parts of the nephron are in which parts of the kidney?
-Glomeruli, bowman’s capsule, proximal + distal convoluted tubules + part of collecting ducts are in the cortex
-Nephron loop (of henle) and rest of collecting ducts are in the renal pyramids
What is the pathway of urine through the kidney?
-From collecting ducts, travels down pyramid to renal papilla (apex of pyramid) to enter minor calyx
-Minor calyces merge with others to form major calyx
-Major calyces merge to form renal pelvis which is continuous with ureter
What does the ureter do and describe it:
-Carry urine to urinary bladder
-Narrow tubes with muscular walls that transport urine via peristalsis
Where do the ureters run?
-Anterior to psoas major on posterior abdominal wall
-Cross pelvic brim to enter the pelvis
-Enter bladder on its inferomedial aspect
What is the typical pain felt from obstructing kidney stone?
-Loin to groin
-Fibres supplying ureters are from T12 to L2 so pain is referred and felt in these dermatomes
Where is the posterior abdominal wall?
-Region behind the abdominal cavity
-Extends from attachments of the diaphragm above to pelvic brim below
What does the posterior abdominal wall consist of?
Lumbar spine together with the psoas and quadratus lumborum muscles
What structures pass along the posterior abdominal wall?
-IVC
-Aorta with associated autonomic plexuses and lymph nodes
-Sympathetic trunks on either side of the lumbar spine
What pass laterally through the posterior abdominal wall?
-Ureters pass down from the kidneys towards the pelvis on surface of psoas muscles
-Gonadal vessels run down over ureters to supply the gonads
What plexus forms on the posterior abdominal wall and what forms it?
-Lumbar plexus
-Lumbar spinal nerves L1-L4 with contribution with T12
What does the lumbar plexus give rise to and what are some notable ones?
-Several branches that innervate the skin and muscles of the abdominal wall and thigh
Notable branches:
-Iliohypogastric and ilioinguinal
-Genitofemoral
-Lateral femoral cutaneous
-Femoral
-Obturator
What do the iliohypogastric, ileoinguinal and genitofemoral nerves innervate?
-Iliohypogastric + ilioinguinal = anterior abdominal wall muscles and skin of external genitalia
-Genitofemoral - skin of external genitalia
What does the lateral femoral cutaneous nerve and femoral nerve innervate?
LFC - skin over lateral thigh
Femoral - large nerve supplies muscles and skin of anterior thigh
What does the obturator nerve innervate?
Supplies muscles and skin of the medial thigh
What is the pathway of the descending aorta?
-Pierces diaphragm at T12 and descends through abdomen as abdominal aorta
-Descends on posterior wall just left of midline
-Terminates by bifurcating into the left and right common iliac arteries at level L4
What does the abdominal aorta give rise to?
-Several paired and unpaired branches
Unpaired:
-Coelic trunk
-SMA
-IMA
Paired:
-renal
-adrenal
-gonadal
-lumbar
What forms the IVC and where?
-Union of left and right common iliac veins
-Approx level of L5
Where does the inferior vena cava ascend in the abdomen and what drains into it?
-Ascends on the posterior abdominal wall just right of the midline
-Veins corresponding to the paired arterial branches of aorta drain into IVC
-EXCEPT left gonadal vein drains into left renal vein
-Also receives hepatic vessels
What are the main functions of the bony pelvis?
-Numerous functions
-Supporting the spine, torso and upper body
-Locomotion
-Housing and protecting the pelvic viscera
What bones make up the bony pelvis?
Three bones:
-Sacrum
-Left and right hip (innominate) bones
What are these and what do they make up?
Bony pelvis
What makes up the hip bone?
Three smaller bones that fuse together:
-Ilium
-Ischium
-Pubis
What do these make up?
Hip bone
What are the articulations of the bony pelvis?
-5 articulations
-Hip joint
-Sacroiliac joint
-Pubic symphysis
-Lumbosacral joint
-Sacrococcygeal joint
Describe the hip joint:
-Between head of femur and acetabulum (socket) of pelvis
-Ilium ischium and pubis of hip fuse at acetabulum
What is this?
Hip joint
Describe the sacroiliac joint:
-Between sacrum and ilium of hip bone
-Very stable and strong and supported by many ligaments
Describe the pubic symphysis:
-Between two pubic bones
-Almost no movement is permitted
Describe the lumbosacral joint:
-Between 5th lumbar vertebrae and the sacrum
-An intervertebral disc lies between the two
Lumbosacral joint
Sacrococcygeal joint
Describe the sacrococcygeal joint:
Between the sacrum and coccyx
Why is this a useful landmark?
-Intercristal line - highest points of iliac crests
-Marks level of L4/L5 disc space used for lumbar puncture
Why is this a useful landmark?
-Line between iliac tubercles (most lateral parts of pelvis)
-Division marking of lower 1/3 of abdomen
What is this and why is it a useful landmark?
-Mid-inguinal point
-Line drawn between ASIS and pubic symphysis
-Femoral artery palpable here
What are the main differences between male and female pelvis?
-Wider, circular pelvic inlet in females / narrower, heart-shaped pelvic inlet in males
-Obtuse angle formed by inferior pubic rami in females, acute angle in males
-Wider and shorter sacrum in females, narrower, longer sacrum in males
What organs does the pelvis contain?
-Organs of the GI and GU systems
-Rectum and bladder in males and females
-Uterus, ovaries and vagina in females
-Prostate and seminal vescicles in males
What do these show?
Contents of pelvis in females
+ovaries
What do these show?
Contents of pelvis in males
What is the main arterial supply of the pelvis?
-Left and right internal iliac arteries
-Give rise to several branches in the pelvis that supply the pelvic viscera
-Some branches exit the pelvis to supply the perineum and gluteal region
Internal iliac arteries
What are the key branches of the internal iliac arteries?
-Vesical - bladder, prostate and seminal vesicles in men
-Uterine and vaginal in females
-Middle rectal - rectum
-Internal pudendal - supplies perineum
-Superior/inferior gluteal arteries - exit pelvis to supply gluteal region
What are these?
4 major branches of internal iliac artery
Major branches of the internal iliac artery
What is the venous drainage of the pelvis?
-Several venous plexuses drain the pelvic organs
-Plexuses unite and mostly drain into the internal iliac veins
In the pelvis, what do sacral spinal nerves form?
Come together to form sacral plexus
What are the key nerves arising from the sacral plexus and at what cords?
-Sciatic nerve - L4-S3 - lower limb
-Pudendal nerve - S2-S4 - perineum
-Superior and inferior gluteal nerves - L4-S1/ L5-S2 - gluteal region
-Pelvic splanchnic nerves - S2-S4 - para to pelvic viscera
label these sacral plexus nerves, which are missing?
Pelvic splanchnic nerves
What is the pelvic floor?
-Collective name for several muscles that support the pelvic organs from below
-Shaped like a bowl or funnel
What are the 3 primary functions of the pelvic floor?
-Prevent herniation of the pelvic organs inferiorly out the pelvis
-Control continence of urine and faeces by providing a sphincter action on urethra and rectum
-Aid in increasing intra-abdominal pressure
What is the pelvic floor made up of?
-Two muscles
-Levator ani and coccygeus
Levator ani composed of 3 smaller muscles:
-Puborectalis
-Pubococcygeus
-Iliococcygeus
What are these?
Muscles of the pelvic floor
Descrive puborectalis muscle:
-U-shaped muscle attaches to pubic bones anteriorly and forms sling around rectum
-Pulls on rectum so sharp angle is formed between rectum and anal canal - prevents defecation
-Relaxes to straighten path from rectum to anal canal
-Contributes to control of micturition
-Most anterior levator ani muscle
Describe the pubococcygeus muscle:
-Lies posterior and lateral to puborectalis
-Attaches to pubic bone anteriorly and coccyx and sacrum posteriorly
Describe ileococcygeus:
-Lies lateral to pubococcygeus
-Attaches to spines of ischium and coccyx
What is the perineum?
What draws its boundaries?
-Immediatly superficial and inferior to pelvic floor
-Superficial region between the pubic symphysis and the coccyx and between the medial surfaces of the thighs
When viewed from below, what does the perineum look like and how an it be divided?
-Roughly diamond shaped and can be split into 2 triangles:
-Anal triangle (post) - opening of anus and external anal sphincter
-Urogenital triangle (ant) - more complicated with several layers
What are the layers of the perineum?
Label these parts of the perineum:
What sits between the two triangles of the perineum?
What attaches to it?
-Perineal body
-Dense mass of fibrous tissue and muscle sits in centre of the perineum
-Acts as attachment for almost all the perineal and pelvic floor muscles including:
-Levator ani
-External anal sphincter
-External urethral sphincter
-Superficial and deep perineal muscles
-Bulbospobiosus
What is common amognst all of these?
All connect to perineal body
Describe the yellow structures:
-Superficial perineal pouch
-Contains most of erectile tissue that unites to form clitoris or penis and muscles overlying them
-Corpora cavernosa are symmetrical + run along ischial rami bilaterally to converge in midline
-Corpora cavernosa connected to ischial ramus called crura of penis or clitoris
Describe the corpus spongiosum of the superficial perineal pouch in men:
-Sits in midline
-Expanded part proximally which rests on perineal membrane
-This is called the ‘bulb’ of the penis
Describe the corpus spongiosum of the superficial perineal pouch in females:
-Sits in midline
-Splits into two parts that flank the vaginal opening and also rest on perineal membrane
-These are called bulb of vestibule (or bulb of clitoris)
What muscles covers what corpora?
-Corpora cavernosa covered by ischiocavernosus muscles
-Corpus spongiosum covered by bulbospongiosus muscle
What muscle is this and what can it help with?
Help stabilise erect penis and clitoris
What muscle is this and what can it help with?
-In males also assists in maintaining erection by compressing veins that drain erectile tissue and contracts to squeeze any remaining urine or semen from the urethra
-In females helps maintain clitoral erection and constricts around vaginal orifice which can help expression of fluid from the greater vestibular glands
What is the arterial supply to the perineum?
-Internal pudendal artery
-Branch of the internal iliac artery
What is this?
Internal pudendal artery
What is this and what does it innervate?
-Pudendal nerve (S2-S4)
-Innervates muscles of the perineum and skin of external genitalia
-Perineal structures also innervated by autonomic nerves in addition to these nerves
What is the pathway of the pudendal nerve and artery?
-Arise in pelvis but don’t enter perineum by piercing pelvic floor
-Travel through greater and lesser sciatic foramina of the pelvis
What are these and what pass through them?
internal pudendal artery and pudendal nerve
What does the vas deferens do up to the pelvis?
Carries sperm from the epididymis up the spermatic cord and through the inguinal canal into the pelvis
What does the vas deferens do past the deep inguinal ring?
-Passes across the side of the wall of the pelvis
-Turns medially onto the back of the bladder
-Here it has a dilated portion - ampulla which lies medial to seminal vesicles
-Terminates by joining duct of the seminal vesicle to form the ejaculatory duct
Label and describe:
-Seminal vesicles
-Each one is a lobulated sac about 4cm long
-Lateral to ampulla of vas deferens
-Secrete a thick alkaline fluid which joins to form the bulk of the seminal fluid
-Duct joins with the vas deferens to become ejaculatory duct which pierces the back of the prostate gland to enter the prostatic urethra
Label:
Describe the top structure:
-Prostate gland
-Roughly spherical fibromuscular gland about the size of a walnut
-Lies against the neck of the bladder and is pierced by the urethra and ejaculatory ducts
-Secretions of the prostate are added to the seminal fluid during ejaculation
What is common about the blood supply of the vas deferens, prostate and seminial vesicles?
All supplied by branches of the internal iliac artery
What organs does the female pelvis exclusively contain?
-uterus
-cervix
-vagina
-uterine tubes
-ovaries
Label and describe:
-Uterus
-Hollow muscular organ
-Communicates laterally with the uterine tubes and inferiorly with vagina
-Has a fundus (above uterine tubes), body and cervix
label and describe the parts of the uterus:
-Body angled anteriorly + lies on superior surface of bladder
-Junction between body and cervix may be tilted anteriorly (anteverted) or posterior (retro-versed)
What happens in the uterus if conception occurs?
-Developing blastocyst implants into the uterine lining (endometrium) in body
-Middle muscular layer (myometrium) becomes distended as pregnancy continues
What is the uterus covered in and its significance?
-Fold on peritoneum
-Adheres to itself at the sides of the uterus to form the broad ligament
Label and describe its significance:
-Rectouterine pouch (pouch of Douglas)
-Space behind the uterus but anterior to the rectum
-Lined with peritoneum
-Deepedt point in the peritoneal cavity so it is a common site for accumulation of intraperitoneal fluid or pus
Label and describe:
-Narrow lumen called the cervical canal which communicates with the uterine cavity and vagina
-Lower part lies inside vagina creating recess - vaginal fornices - around the cervix
Label and describe what they connect:
-Internal os - communication with uterine cavity
-External os - communication with vagina
Label and describe what they connect:
-Internal os - communication with uterine cavity
-External os - communication with vagina
What are these created by?
-They are the vaginal fornices
-Created by cervix lying inside the vagina creating a recess
What is the cervix stabilised by?
-Position of the cervix is stabilised by the tone of the levator ani muscles and ligaments
-Run from lateral wall of cervix to the lateral pelvic wall at the base of the broad ligament
Label and describe:
-Fallopian tubes
-Carry ova from ovary towards uterine cavity
-Fertilisation occurs inside these tubes
-Found running in upper border of broad ligament
Describe the shape of the uterine tubes:
-Near the uterus they have a narrow isthmus
-Laterally the tubes have a dilated ampulla leading into a funnel-shaped infundibulum
-Free edge of infundibulum is broken up into finger-like projections (fimbriae) draped over the ovary
Label and describe:
-Almond-shaped
-Almond-shaped
-Attached to the posterior aspect of the broad ligament by short mesentery -> mesovarium
-Mesovarium
-Short mesentery connecting the ovary to the posterior aspect of the broad ligament
Describe the position of the ovaries and what other structures they are in relation to:
-Not fixed
-Frequently lies in ovarian fossa -> formed by the angle between the internal and external iliac arteries
-Ureter and obturator nerve and vessels are close relations of the ovarian fossa
What are these and what do they mark the boundary of?
Ovarian fossa
Label and describe:
-Female organ of sexual intercourse and excretory duct of the uterus
-Passes through the pelvic floor, upper 2/3 of the vagina lie in the pelvic cavity and lower 1/3 in perineum
What are the two ends of the vagina?
-Blind-ended vault in the region of the cervix
-Terminates below at the introitus by opening into the vestibule between the labia minor
What is the vagina closely related to?
-Bladder anteriorly
-Urethra is often embedded in the anterior wall of the lower 1/3 of the vagina
What is the vessel in green?
-Ovarian artery
-Direct branch of abdominal aorta
What is the vulva?
Collective term for all of the parts of the female external genitalia
What is the blood supply to the vulva?
Mainly via the internal pudendal arteries -> branches of internal iliac arteries)
What is the innervation of the vulva?
-Four nerves:
-Ilioinguinal nerve
-Genital branch of genitofemoral nerve
-Pudendal nerve
-Posterior cutaneous nerve of the thigh
THE ERECTILE TISSUE ARE INNERVATED BY PARASYMPATHETIC NERVES
Label:
What does this show?
Nerve supply to the vulva
Label:
What are they all part of?
Vulva
Label and describe:
-Area between labia minor
-Contains vaginal opening, urinary meatus and vestibular glands
Label and describe:
-Vestibular glands
-Greater (Bartholin’s) - just posterior to vaginal opening and secrete lubricant into the vagina during sexual arousal
-Lesser (Skene’s) - near urehtral opening, function of their fluid is debated however may lubricate vaginal opening or urehtra or have antimicrobial affect
label and describe:
-Thin membrane that partially covers vaginal opening
-Often ruptures during first episode of sexual intercourse
-Can rupture spontaneously -> exercise, tampons, menstrual cups
-May be absent altogether
What is the mons pubis?
Elevation of fatty tissue located in front of pubic symphysis causing an elevation of the hair-bearing skin
What are the labia major and minora?
-Majora - prominent hair-bearing folds of skin that meet at mons pubis anteriorly
-Minora -
-Smaller, hairless folds of skin located medial to major
-Fuse together anteriorly to form hood of clitoris
-Boundaries of vestibule
What is the clitoris?
-Pea-sized highly sensitive tissue comprised of erectile corpora cavernosa and spongiosum
-Engorged during sexual arousal
What is the vaginal opening?
Anatomical name?
Entrance to the vagina also known as the vaginal Introits
What is the urinary meatus?
-Opening of urethra
-Lies posterior to the clitoris but anterior to the vaginal opening
What is this?
What is its position?
-Urinary bladder - hollow muscular organ
-Located in the pelvis below the peritoneum (infra-peritoneal organ)
-Posterior to pub symphysis and anterior to the vagina and rectum
What is the blood supply of the bladder?
-Vesical arteries - branches of internal iliac
-Vesical veins draining into internal iliac vein
What are the arteries in green and their respective veins?
Vesical arteries and veins
What is the function of the bladder and how does it do this?
-Stores urine and helps squeeze the urine out during micturition
-When empty, bladder may squash down completely
-When full, superior aspect may extend above the pubic symphysis
-Can accomodate approx 400-600ml of urine in an adult
What fills the bladder with urine and from where?
What is this area called?
-From ureters
-Drain into posterior aspect of bladder near base
-This triangular area is called trigone and has smooth wall
How do the ureters enter the bladder and what is the significance of this?
-Enter the trigone at an angle
-Forms a rudimentary valve which prevents reflux of urine into the ureters when bladder is full
Describe the inside wall of the bladder:
-Trigone = smooth walled
-Rest = corrugated with folds of mucosa called rugae
-Allow bladder to stretch without tearing when it fills
-Walls contain smooth muscle (detrusor) which contracts to forcibly expel urine
What are these and what do they control?
Describe them:
-Release of urine
-internal = base of bladder where it opens into urethra, composed of smooth muscle and involuntary
-External = located just after the prostate in males and deep perineal pouch in females, skeletal muscle under voluntary contro
Describe the somatic innervation to the urinary bladder and urethral sphincters
-Branches of the pudendal nerve (S2-S4)
-Allows conscious control of external urethral sphincter
Describe the sympathetic innervation of the urinary bladder and urethral sphincters:
-Branches of hypogastric nerve (symp chain T12-L2)
-Causes relaxation of teh detrusor and contraction of the internal urethral sphincter allowing storage of urine
Describe the parasympathetic innervation to the bladder and urethral sphincters:
-Pelvic splanchnic nerves (S2-S4)
-Causes contraction of detrusor and relaxation of the internal urethral sphincter allowing initiation of micturition
What is the urethra split up into in men?
-Preprostatic
-Prostatic
-Membranous
-Penile
What is the bladder reflex arc?
-As bladder fills, stretch of bladder wall is detected
-Relayed to sacral spinal cord via visceral afferents
-These synapse directly with motor neurons
-Motor neurons (via pelvic splanchnic parasympathetic fibres) stimulate bladder contraction
In older children and and adults, what happens to the urine reflex arc?
-Inhibited by inputs from the cerebral cortex
-Older children and adults can detect bladder filling and consciously control when and where to urinate
-‘potty training’ = infants learn to consciously recognise bladder filling and develop descending pathways that inhibit the reflex
What is the rectum?
-Terminal part of the large intestine
-Two notable curves (flexures)
-One anteriorly - sacral flexure
-Posteriorly - anorectal flexure
-Storage of faeces prior to defecation
12cm
What is the most distal part of the gastrointestinal tract and where does it extend from?
-Anal canal
-Distal rectum to anus
-Lies in anal triangle of perineum
What control defecation?
-Two anal sphincters
-internal = smooth muscle + involuntary
-external = skeletal muscle + voluntary
What is this and what does it do?
-Pectinate line (dentate line)
-Divides superior part of anal canal from inferior
-Superior = endoderm derived
-Inferior = ectoderm derived
-Supplied by different vessels
What is the blood supply above the pectinate line?
-Part of the hindgut
-Supplies by inferior mesenteric artery (via superior rectal artery)
-Venous drainage via the portal venous system
What are the vessels in green?
Superior rectal arteries
What encircles the superior part of the anal canal?
Describe its innervation:
-Lined by columnar epithelium
-Encircled by internal anal sphincter (involuntary)
-innervated by sympathetic fibres from sympathetic trunk and parasympathetic fibres from the pelvic splanchnic nerves
What is the blood supply to the inferior anal canal?
-Middle and inferior rectal arteries which originate from the internal iliac arteries
-Venous blood enters the systemic venous system
What are the vessels in green and the ones below?
Middle and inferior rectal arteries
What is the inferior anal canal encircled by?
What is this innervated by?
-Stratified squamous epithelium lines lumen
-External anal sphincter - voluntary
-Innervated by the pudendal nerve - somatic
What is this?
Pudendal nerve
