Pelvis

Question 1

Floor of the Inguinal Canal

Answer 1

The Inguinal Ligament- This is the rolled up aponeurosis of External Oblique Muscles. On it’s lateral side there is the transversalis fascia

This is thickened by Lacunar Ligament

Question 2

The Roof of the Inguinal Canal

Answer 2

Internal Oblique - Lateral two-thirds of Inguinal Ligament; they arch medially and downwards. Into flat aponeurosis, passing in front of rectus abdominis. and then moves laterally into pectineal line up to as far as the lacunar ligament.

Transversus Abdominis- in the Lateral Half of the Inguinal Ligament. In fibres of internal oblique.

These two muscles join and form the conjoint tendon@ pectineal line.

They are supplied by the ilioinguinal and iliohypogastric nerve(L1). Incision causes direct inguinal ligament above this, But if injury of ilioinguinal nerve occurs IN the inguinal canal only sensory changes of the ant. part of scrotum or labia majora occurs as the motor branch has already been given off

Question 3

Posterior wall of Inguinal Canal

Answer 3

Transversalis fascia

Medially the conjoint tendon also provides support

• it is also strengthened by fibres called interfoveolar ligament (around medial end of deep ring) which is thickened tissue of the trasnversalis fascia & lie in front of inf. epigastric arteries

Question 4

Describe location of deep inguinal ring

Answer 4

lies above the midpoint of inguinal ligament & is an opening of transversalis fascia when it is pulled like a sleeve becomes internal spermatic fascia.

Question 5

Structures around deep inguinal ring & course of inf. Epigastric Artery

Answer 5

Medial to it is the inferior epigastric(branch of external iliac artery)

Lateral to Interfoveolar ligament lies the Vas deferens/ Broad ligament which hooks around it and then enters the canal

The course of the inferior epigastric vessels go from deep to trasversalis fascia perforates this and goes upwards medially and into rectus sheath behind this. It also gives off a cremasteric branch next to the deep inguinal ring. It also provides branches to periosteum of pubic ramus called pubic branch & anastomoses with pubic branch of obturator artery.*

• if obturator artery not present will open up to form accessory/abnormal obturator artery

Question 6

What are the borders of Hesselbachs triangle & it’s significance

Answer 6

Medial: Rectus abdominis
Lateral: inferior epigastric artery
Below: Inguinal Ligament

Hernia Lateral to Lateral Border: Indirect Hernia into Inguinal Canal

Hernia Medial to Lateral Border: Direct hernia into conjoint tendon

Question 7

Contents of spermatic cord

Answer 7

3 coverings and 6 groups

3 coverings
i. Internal Spermatic Fascia(deepest)
(Transversalic fascia)
ii.Cremasteric Fascia With cremaster muscle
(Transversus muscles follows this and attaches to pubic tubercle
iii. Superficial Spermatic Fascia
Contents:
1. Testicular veins
2.Testicular artery
3.Artery for vas deferens( from superior or inferior vasical)
4.Pampiniform plexus
5. Vas deferens- Posterior and lower part of cord
6.processus vaginalis- obliterated if patent is the pouch for indirect inguinal hernia
7. autonomic nerves- genital branch of genitofemoral nerve
8. Lymphatics-> to paraortic
9*.Spermatic cord/ Broad Ligament
10**.Ilioinguinal Nerve

• does not enter via deep ring between internal and external oblique muscles- then leaves and supplies the upper part of the thigh and ant. third of the scrotum

Question 8

The layers of the testis; nerve supply of the testis

Answer 8

2 layers

i. Tunica Albuginea(deep layer)
ii. Tunica Vaginalis

nerve supply:
Sympathetic fibres of T10 via greater or lesser splachnic nerves nil parasympathetic

Question 9

Structure of the testes and Histological description of Testes

Answer 9

• mediastinum testis where the septa lies to reach the tunica albuginea
• septa divides the testes into 400 lobules which contain a few seminiferous tubules which open into rete testis(a network of intercommunicating channels)

Histology
Convoluted seminiferous tubules (within the lobules) → straight seminiferous tubules (near mediastinum testis) → rete testis (within mediastinum testis) → efferent ductules → epididymis → ductus deferens → ejaculatory duct → prostatic urethra

Cells at Straight Seminiferous Tubules have spermatogonia occuring where primary spermatocytes occur–> secondary spermatocytes ->spermatids which metamorphasizes into spermatozoa

Sertoli cells-> release ABP maintains high testosterone environment
Leydig cells-> secretes testoterone
Testis make small amounts of semen

Question 10

Embryological origin of the testes

Answer 10

gonadal ridge medial to the mesonephric ridge of the intermediate cell mass

Question 11

What are the muscles of the true pelvis

Answer 11

obturator internus and piriformis
levator ani and coccygeus

Question 12

What is the origin and insertion and innervation of pifirormis

Answer 12

Origin: From the lateral mass of the sacrum
Nerve to pirifromis from the sacral plexus
-covered in fascia

Question 13

What is the origin and insertion of levator ani

Answer 13

the levator ani is made of three muscles, pubococcygeus, puborectalis, and ileococygeus and its origin is from body of the pubis to the ischial spine and contains a medial spinous plate
i.pubococcygeus comes from arises from the tendinous arch and the posterior surface of the body of the pubis
ii.Puborectalis -originates from the posterior surface of the pubis and forms a U-shape. innervated by the pudendal nerve and nerve to levator ani
iii.Ileococcygeus- originates from the ischial spine and the posterior tendinous arch of the obturator internus and inserts into coccyx perineal body and anococygeal ligament.

Question 14

What is the origin of the coccygeus and it’s insertion?

Answer 14

arises from the ischial spine, and inserts itself

Question 15

What is the course of the rectum

Answer 15

The rectum is a continuation of the sigmoid colon at around S3, the sigmoid mesocolon ends and the rectum has no mesentery but is covered in fat more bulky posteriorly. The teania coli at this point broadens out into anterior and posterior segments which meet laterally to complete an outer layer of longitudinal muscle. Hence there are no sacculations of the rectum. The rectum turns downwards and backwards as the anal canal at the coccyx and slung forward by puborectalis. Near the top of the anal external sphincter. The superior rectal artery and superior rectal vein. On the upper part there is mesentary anteriorly and its side and middle third there is some anteriorly and the bottom third only has a forward reflection forming the recto/vesicouterine pouch.

Question 16

What is the content of the rectovesical pouch?

Answer 16

In front of the rectovesical pouch uppermost base of the ureter and the top of the seminal vesicle, below this is the prostate, ends of vas deferens and ureter

Question 17

What is the blood supply of the rectum

Answer 17

The rectum is supplied by:
i.Superior rectal artery(A division of the inferior mesenteric artery)- gets it’s name when entering the pelvic brim and crosses the LEFT common iliac artery MEDIAL to the ureters @S3 veterbra it divides into left and right
ii.Inferior rectal artery(pudendal artery from internal iliac artery)- will anastomose with i. at the submucosal layer of the rectum
iii.middle rectal artery
It’s venous supply corresponds to its arteries but is free to anastomose and does so submucosally(internal rectal plexus) and the muscular wall(external rectal plexus) and drains from the i.superior rectal vein via inferior mesenteric veins in between the artery and ureter.
ii.inferior rectal vein drains via the internal pudendal veins

Question 18

What is the lymphatic drainage of the lymph nodes

Answer 18

Lymphoid follicles in the mucous membranes drain to epiploic nodes on the surface of the rectum and perorectal nodes of the mesorectum.
Superior rectum -
inferior rectum- internal iliac nodes

Question 19

What is the nervous supply of the rectum

Answer 19

Sympathetic plexus comes from the inferior mesenteric plexus
Parasympathetic supply is via pelvic splachnic nerves from S2-S4 via the inferior hypogastric plexus(motor and stretching sensation muscles)

Question 20

Describe the bladder

Answer 20

The bladder is a pyramidal shaped structure in the pelvic brim with it’s apex facing the pubic symphysis and has a urachus attached to it forming the median urachus. The posterior wall lie in front of the rectum/vagina. The inferolateral wall lie in front of obturator internus, and the lowest part of the bladder, the neck which is pierced by the urethra at the internal urethral orifice/base of prostate for the males.

Question 21

What is the trigone of the bladder?

Answer 21

The trigone is a section of the bladder found on the base, which is triangular in shape. It has two uretheral orifices at the top laterally and a ureteral orifice centrally and below. It is fixed with connective tissues in the women anteriorly of the vagina and the prostate in men. It is smooth walled and the mucus membrane is firmly attached to the underlying muscle. The orifice is connected by a firm muscular ridge termed the inteureteric bar The urethral pierce the muscle obliquely thus preventing reflux of urine. It also contains a superficial muscle underneath extending into the urethra. It i

Question 22

What is the blood supply of the vas deferens and seminal vesicles

Answer 22

The blood supply of the vas deferens is via the artery of the vas deferens a branch of the superior OR inferior vesical artery. Seminal vesicles via branches of the middle rectal and inferior vesical arteries

Question 23

What are the basic information of the prostate?

Answer 23

• Is is a fibromuscular organ lying below the bladder but above the pelvic diaphragm, and is penetrated by a urethra. It provides about 30% of seminal fluid. Its structure is described as having a base, an apex, posterior and inferolateral surfaces. Its base is the upper surface fused with the neck of the bladder. The apex is the LOWEST part. Where the pierced prostatic urethra then perforates through and becomes the membranous urethra, surrounded by sphincter urethrae. The inferolateral area is clasped by the pubourethalis of the levator ani and the anterior region is behind the retropubic space and is connected to the body of the pubis via puboprostatic ligaments. The posterior surface is in front of the rectum but separated by retrovesical fascia The ejactulatory ducts pass through prostate and travels obliquely into the prostatic urethra. There is a strong layer of connective tissue called the capsule, in the periphery of the glands, and outside there is a false capsule. Between these layers are the vesicoprostetic plexus of the veins.

Question 24

What is the prosthatic urethra?

Answer 24

• It is a continuation of the urethra as it passes through the apex of the prostate. It runs downwards and backwards from the internal meatus, there a midline ridge termed the urethral crest from the posterior wall forming two shallow depressions termed the prostatic sinus. At the midline of the sinus a seminal colliculius/verumontanum forms a rounded eminence. Where a prostatic utricle which is a small recess represeiting the fused ends of the Mullerian ducts & the ejaculatory part lies there as well.

Question 25

What is the blood supply of the prostate?

Answer 25

• The main blood supply is from the prostatic branch of the inferior vesical artery
  ii.Middle rectal
  iii. Internal pudendal artery
• The venous drainage is via the plexus in between the true and false capsule which then drain into vesicoprostetic plexus between the bladder and prostate this plexus also receives the dorsal vein and into the internal iliac vessels

Question 26

What is the nerve supply of the prostate

Answer 26

The acini receive parasympathetic innervation via pelvic splachnic nerves via the inferior epigastric plexus and the muscle fibres of the stroma receive sympathetic control for ejactulation also via the inferior epigastric plexus via(adrenergic channels)

Question 27

What is the course of the vas deferens?

Answer 27

• The course of the vas deferens is as a continuation of the epididymis. And enters the abdomen at the deep inguinal ring passing along the side wall and floor of the pelvis to reach the back of the bladder. It then courses behind the interforveolar ligament and the inferior gastric vessels in the deep inguinal ring and also crosses the external iliac artery and vein, the obliterated umbilical artery and obturator nerve,artery and vein on the obturator fascia. Then goes medially forwards above the ureter. And now turn downwards and becomes fusiform forming the ampulla. The ampula lies parallel and medial to the seminal vesical.

Question 28

What is the course of the seminal vesicles?

Answer 28

The seminal vesicle is a thin-walled, elongated sac, like a lobulated, blind-ending tube much folded on itself. The pair produce about 60% of the seminal fluid, and are applied to the base of the bladder above the prostate.The rectovesical fascia lies behind them and their tops are just covered by the peritoneum of the rectovesical pouch. Each lies lateral to the ampulla of the vas deferens of its own side, and at the lower end of the ampulla behind the prostate the duct of the seminal vesicle joins the vas to form the ejaculatory duct.

Question 29

What is the nerve supply of the vas and seminal vesicles?

Answer 29

The smooth muscle of the vas and seminal vesicles receives fibres from the inferior hypogastric plexus. They are mainly sympathetic motor fibres from the first lumbar ganglion via the hypogastric plexuses; their division produces sterility, for the paralysed muscle cannot contract to expel the stored secretion and spermatozoa, i.e. there is no emission or ejaculation

Question 30

Describe the Uterus?

Answer 30

It consists of a fundus which is superior to the entrance of the fallopian tubes. it possesses a serous coat of pelvic peritoneum, which then continuous downwards over the front and back of the body.
-The body tapers downwards from the fundus and is flattened, superiorly it has a cornu which is at the junction of the body and fundus there lies the fallopian tubes. It too is covered with a peritoneum, where laterally it becomes the broad ligament. Lastly is the cervix, which has a vaginal and supra vaginal part. The deep sulcus surrounds the protruding cervix is the fornix of the vagina. It too is covered by the peritoneum ONLY posteriorly. forming the anterior part of the pouch of douglas. anteriorly, it is bound to the trigone by dense connective tissues with no peritoenums. The cervix has a canal with an external os usually level with the ischial spines.

Question 31

Describe the uterine tubes.

Answer 31

The tube is 10cm long. 1cm(intramural) is embedded in the uterine wall. Then, the tube lies in the upper edge of the broad ligament, called the mesosalpinx, in a straight fashion called the isthmus. Then the ampulla forms half the length of the tube, and finally the infundibulum with fimbriae at the end which is connected to the ovary, this lies behind the broad ligamens adjacent to the lateral pelvic wall.

Histologically, There is two layers an inner circular and outer longitudinal. It is lined by a mucous membrane thrown into folds. and has a surface epithelium which is a mixture of ciliated and non ciliated COLUMNAR cells. The internal layer is the myometrium which is described as 3 layers . Outer muscles are longitudinal while the inner muscles are round in nature, and act as sphincters. the mucus membrane is the endometrium which has a columnar epithelium.

Question 32

What is the blood supply of the uterus and uterine tubes

Answer 32

i. Uterine Artery- branch of the internal iliac.
- it passes medially across the pelvic floor @ the base of the broad ligament ABOVE the ureter, where it reaches the sides of the supravaginal side of the cervix, where it gives a branch to the vagina and cervix. Then it curves upwards in a tortous manner towards the cornu giving off branches. At the junction of the body and fundus it moves laterally and anastamoses with the overian artery supplying the uterine tube.
venous return is via veins of the uterus which lie under the artery and form a wide plexus across the floor and communicates withthe vesical and rectal plexus to the internal iliac veins

Question 33

What is the lymphatic drainage of the uterus

Answer 33

at the cervix, Via the external and internal iliac nodes and the sacral nodes along the uterosacral ligaments. the lowest part of the uterine body drains into the external iliac nodes, and the rest of the body and fundus drains into the para-aortic nodes.

Question 34

What is the nerve supply of the uterus like?

Answer 34

Branches of the inferior hypogastric plexus. Sympathetic response is as a vasoconstrictor and facilitates uterine contract. Pain is via pelvic splachnic nerves. but pain in the supravaginal cervix and uterus is via sympathetic nerves at the level T10-L1

Question 35

Describe the broad ligament and it’s content

Answer 35

It is the ligament surrounding the lateral uterus. It’s medial edge lies on the side wall of the uterus and flows over the intestinal side as well, its lateral edge isattached to the side walls of the pelvis. the inferior edge lines the pelvic cavity with the ureters beneath it. It also covers the obturator nerve and vessels, superior vesical and obliterated umbilical vessels.Finally laterally it also contains the ovarian vessels and lymphatics over the external iliac vessels called the suspensory ligament of the ovary.

The anterior layer bulges forward by the round ligament of the uterus below the uterine tube, and the posterior layer suspends the ovaries as the mesovarium, and finally the parametrium where the uterine vessels and luymphatics lie.

Question 36

What is the round ligament

Answer 36

It is a ligament extending from the junction of the uterus to the deep inguinal ring and lies IN the broad ligament BELOW the uterine tube. it is continuous with the ligement of the overy. representing the gubernaculum, passing through the inguinal canal and is also attached to the tissue of the labium major. it is supplied by the ovarian artery IN the broad ligament, and the inferior epigastric artery at the inguinal canal. The ligament keeps the uterus in anteflexion and anterversion.

Question 37

what is the transverse cervical ligament

Answer 37

This is the main ligament which provides support to the cervix and vagina. it is formed as thickening of the base of the broad ligament, from the cervix to the vaginal fornix laterally. The ureter, uterine artery and inferior hypogastric plexus traverse these ligmanet.

It also consists of the uterosacral ligaments containing fibrous tissue and smooth muscles coming backwards from the cervix below the peritoneum and embracing the rectouterine pouch of the rectum and into the front of the sacrum. This prevents the cervix from being pulled forwards

Question 38

What ligaments hold the ovary in place

Answer 38

The ligament of the ovary hold the inferior border of the ovary towards the uterus. it is continuous with the round ligament and is attached to the cornu of the uterus, are also part of the remnants of the gubernaculum. The anterior head of the ovary is also covered by the posterior part of the broad ligament forming the mesovarium. The lateral surface of the ovary lies in the angle of the internal and external iliac vessels. the parietal peritoneum separates it from the obturator nerve and ureter.

Question 39

What is the course of the ovarian artery

Answer 39

It comes directly off the branch of the aorta below the renal artery. it runs behind the peritoneum of the infracolic vessels and crosses the ureter obliquely. on the psoas muscle.crosses the pelvic brim and enters the suspensory ligament of the broad ligaments. it also passes a branch to the uterine tube between the broad ligaements anastamosing with the uterine artery.
venous return is via the pampiniform plexus of the mesovarium. into the ovarian veins finally draining into the L) renal vein or directly to the inferior vena cava

Question 40

Describe the lymphatic drainage of the ovary

Answer 40

• Preaortic nodes at the origin of the overian artery L2.

Question 41

What is the nervous supply of the ovaries

Answer 41

Sympathetic response lies in the aortic plexus along the blood vessels. the preganglionic cell bodies in T10-11. Sensory sensation comes from this.
Parasympathetic response comes from the inferior hyopogastric plexues along the uterine artery

Question 42

Describe the ovary

Answer 42

It consists of a inner vascular medulla and outer cortex, encapsulated with a fibrous connective tissue(tunic albuginea). Which is also covered by a layer of cuboidal cells, the surface epithelium

Question 43

Desribe the vagina and include it’s blood supply and innervation

Answer 43

It is a fibromuscular tube directed upwards and backwards. It lies in front of the rectum, separated by the rectovaginal fascia and a rectovaginal septum below this, the perineum and anal canal but posterior to the bladder and urethra. The upper end has a anterior and posterior fornix with the posterior deeper and covered in peritoneum. The ureter is adjacent to the lateral fornix and then the ureter passes across to the anterior fornix to enter the bladder. The vagina passes through the pubovaginalis of lavator ani into the superficial labia minora. in between this space lies the bartholins gland below the hymen of the posterolateral wall. With the urethra lying in front of the vaginal orifice.

Blood supply via the vaginal branch of the internal iliac artery supplemented by the uterine, inferior vesical and middle rectal vessels. Venous return is via the plexus of the pelvic floor intot the internal iliac vein.

Its innervated by the branches of the pudendal nerve and anteriorly by the ilioinguinal nerve. the inferior hypogastric nerve controls the blood vessels and smooth muscles of the vafginal wall. Histologically, the vagina, has a muscular layer of smooth muscle lined by mucus membrane(stratified squamous non keratinizing) and fibrous tissue externally lined with the pelvic fascia. except at the posterior fornix

Question 44

What is the blood supply of the female urethra

Answer 44

The blood supply of the urethra is via internal pudendal and inferior vesical and vaginal arteral superiorly

Question 45

What is the histological description of the urethra

Answer 45

Lined by non keratinized stratified squamous epithelium, which have few mucous glands on the wall. They have paraurethral glands which is analogous to the prostate and has some muscle fibres from the trigone superiorly. The muscles is oriented longitudinially which when contraction occurs causes widening of the lumen and shortening of the urethra. Outside, there are striated circular muscles of the shinter urethra. it is thickest anteriorly and in the middle of the urethra. supplied by the pudendal nerve

Question 46

What is the course of the Internal iliac arterty

Answer 46

The common iliac artery bifurcates at the pelvic brim next to the SI joint. it then goes downwards into a sort posterior and longer anterior division.

The posterior has 3 vessels
i.Superior gluteal
ii.Iliolumbar
iii.Lateral sacral

the anterior have 9 vessels
i. Superior vesical
ii. Obliterated umbilical
iii. infererior vesical
iv.Obturator
v. internal pudendal
vi. Inferior gluteal
vii.middle rectal
viii.uterine
ix. vaginal

Question 47

What are the divisions of the posterior internal iliac vessels?

Answer 47

i.The Iliolumbar- Passess upwards out of the pelvis infront of the lumbrosacral trunk and behind the obturator nerve DEEP to the psoas muscle. the Lumbar branch then supplies psoas and quadratus lumborum and finally the erector spinae. it also gives a spinal branch into the L5 foramen and the sacrum
The ileal branch supplies the iliac fossa, it extends to the anastamosis of the ASIS(deep and sup. circumflex arteries, ascending branch of lat. circumflex femoral and upper branch of superior gluteal artery

ii.Lateral Sacral artery- runs lateral to the anterior sacral foramen infront of the roots of the sacral plexus. it supplies this and the piriformis. it also enters and supplies the ant. sacral foramina supplying the spinal meninges and roots to exit at the posterior sacral foramina to supply the segmental supply of the lumbar arteries

iii.Superior gluteal artery-passes backwards

Question 48

Describe the anterior divisions of the internal iliac artery

Answer 48

i. Superior vesical artery- the proximal part runs along the side wall of the pelvis and then turns medially to reach the bladder and also supplies the ureter and the vas deferens
ii.Inferior vesical artery- also runs medial to the pelvic floor to supply the trigone and bladder, the ureter and vas deferens, seminal vesical and prostate.
iii.Middle rectal artery- a small artery supplying the rectum, and may be absent sometimes being replaced by another branch
iv. uterine artery- ABOVE the ureter in the base of the broad ligament. at the cervix, it turns upwards alongside the uterus and at the entrance of the uterine tube turns laterally supplying the utbe and anastomosing with the obturator atery

v. Vaginal artery- goes with the inferior vesical artery analogous to the inf. vesical artery

vi.Obturator- goes along the side of the pelvis below the nerve and enters the obturator foramen, with the neurovascular bundle. the artery gives a small branch at the back of the piubis and anastamoses with the pubic branch of inferior epigastric.

vii.Inferior Gluteal artery- passes below the piriformis in the greater sciatic foramen, below S1 root

viii.Internal pudendal artery- Infront of inferior gluteal and pierces the parietal pelvic fascia also below piriformis and into the perineum to the anal and external genitelia

Question 49

What is the course of the internal iliac vein

Answer 49

It initially forms as a confluence of rectal vesical/uterine or prostatic /vaginas plexus and all the subsequent branches of the arteries which occurs at the greater sciatic notch and goes upwards posteromedially to join the external iliac vein on the medial surface of psoas, forming the common iliac veins. it also communicates with the vertebral venous plexus at the lateral sacral veins

Question 50

What is the sacral plexus

Answer 50

It is apart of L4,L5 which forms the lumosacral trunk. which passes over the ala of the sacrum and crosses the pelvic brim medial to obturator which is separated by the iliolumbar artery and vein. It lies on the piriformis muscle from the anterior foramina of the sacrum as is covered by the peritoneal fascia. In front of this is the lateral sacral vessels.

Question 51

What is the location of the hypogastric plexus and its components

Answer 51

An autonomic plexus on the side wall of the plexus on each side. In the male it is lateral to the rectum and posterolateral to the seminal vesicle, prostate, and bladder. in the female, it is lateral to the rectum cervix, vaginal and posterolateral to the rectum.

Sympathetic components from the superior hypogastric plexus(hypogastric nerve), and sacral sympathetic ganglia
Parasympathetic components are from preganglionic(myelinated) fibres from S2-S4(pelvic splachnic nerve). half then relay in the ganglia and the rest continue without relay.

Question 52

Where do the parasympathetic motor and secretomotor fibres of the inferior gastric plexus relay

Answer 52

In the walls of the viscera

Question 52

What innervates the detrusor and rectum?

Answer 52

The parasympathetic nerves from the pelvic splachnics.

Question 53

What do the superior hypogastric plexus from the INFERIOR hypogastric plexus supply

Answer 53

the bladder neck, prostate, seminal vesicle and vas deferens. this is a SYMPATHETIC supply

Question 53

What does the sacral sympathetic ganglia supply

Answer 53

The internal sphincter of the anal canal

Question 54

What nerve supplies the anal region

Answer 54

Inferior rectal nerve(S3-S4 cutaneous nerves)
Perineal branch of S4
Twigs of coccygeal plexus(S5)

Question 55

Describe the anus

Answer 55

The anus is the last part of the alimentary canal measuring about 4cm. it consists of circular tube of muscles and an internal and external anal sphincter. They are usually closed except during the passing of feaces and flatulence. and this is aided with the mucous membrane. The junction of the anus to the rectum is at the pelvic floor(Levator ani/puborectalis)

Question 56

Describe the external anal sphincter

Answer 56

It contains a deep, superficial and cutaneous part
in it’s upper end there is a blend of the puborectalis and the external anal sphincter. an area called the anorectal ring, except anteriorly where there are no levator ani muscles. Then the middle parts move backwards towards the coccyx cotributing to the anococcygeal ligament. and in between this and the iliococcygeal raphe called the retrosphincteric space.
The lowest part, curves downwards below the internal sphincter.This submucosal apposition of the two sphincters is at the site of the palpable intersphincteric groove in the lower part of the anal canal.

Question 57

Describe the internal anal sphincter

Answer 57

Continuous muscle fibres of the circular muscles of the rectum.At the anorectal junction the outer longitudinal layer of rectal muscle becomes fibroelastic and, together with some striated muscle fibres of puborectalis, forms the conjoint longitudinal coat which runs down between the two sphincters.

Question 58

Describe the histology of the mucus membrane of the anus

Answer 58

In the upper third of the anal canal the mucous membrane shows 6 to 10 longitudinal ridges, the anal columns . At their lower ends adjacent columns are joined together by small horizontal folds, the anal valves ; the pockets so formed above the valves are the anal sinuses , into which open mucus-secreting anal glands . About half the anal glands are submucosal and the rest penetrate through the internal sphincter. he level of the anal valves is the pectinate line (also called the dentate line) below which is a pale, smooth-surfaced area, the pecten, which extends down to the intersphincteric groove. Below the groove is a truly cutaneous area, continuous at the anus (anal margin) with the skin of the buttock.

Histologically the lining below the groove is keratinized stratified squamous epithelium, hair follicles, sebaceous glands and sweat glands. The lining of the pecten is non-keratinized stratified squamous epithelium, with no hair follicles, sebaceous glands or sweat glands.

The anal column area, being continuous with rectal mucosa, has typical columnar intestinal cells and tubular glands. But immediately above and below the pectinate line there is a zone of variable, often mixed epithelial structure, so that there is no abrupt line of change from the single-layered gut type to multilayered pecten type.

Small submucous masses, comprising fibroelastic connective tissue, smooth muscle, dilated venous spaces and arteriovenous anastomoses, form anal cushions at left lateral (3), right posterior (7) and right anterior (11 o’clock) positions in the upper anal cana

Question 59

What is the blood supply of the anus

Answer 59

Branches of the superior rectal artery supply the upper end of the canal, their terminations lying within the anal columns. A small part of the muscular wall is supplied by the median sacral arteries, while the lower end, including its mucous membrane, receives the ends of the inferior rectal vessels which have crossed the ischioanal fossae. Within the walls there is good anastomosis between the various vessels.

The veins correspond to the above arteries and are continuous with the rectal venous plexuses (see p. 294 ). The upper part of the canal and plexus drains via the superior rectal and inferior mesenteric veins to the portal system, whereas the lower end drains to the internal iliac veins through the inferior and middle rectal veins. The anal canal is thus a site of portal–systemic anastomosis (see p. 267 ), the union being in the region of the anal columns.