GIT Anatomy Coursework Materials

Small intestine Small intestine is the principle site for absorption of nutrients Digestion maintaining of the fluid for hameeshuses endacon & immune sytem Qraminal ileum absorb B12, FA, bile sults Q Emberyology: 4th week endoderm form →primitive gut lube fergut Protonal doodeeum Smal mid gut all intestine & except protumal d hind gut *endoderm bekome intestinal epithelium & glands." *mesodeum become Connective tissue, muscle, wall of intestine (5th week intestine elongate & midget bap herniate thiough wimbilical ring. (10 th week! midgut loop colales 270 Countericek wise around the axis of superior mesenteric artery and return back into abdomin Anatomy atomy-total length 5-10 m -Intestinal prishalisis (contraction) at rule of 1-2 cm/sec to move chyme through intestine (6 min avarage) -Duodenum (25 cm) jejunum (100-110 cm) ileum (150-160 (m) *Duodenum Retroperitoneal structure. (No mesentery (stence) Jejusum silaum intraperitoneal structure. -Small bowed is supplied by branches of superior mesenteric artery. lymphatics also participate in atcorption of flat)) bowel wall mesenteric nodes lymphatic Vessels fouled to corresponding actories Cisterna chylt (retro perilored strucdeive) belaveen corde ve thoracic duct left subclavian Vein nerve supply: * Parasympathetic fibers from vagus & Celiac gangha (barel secration - motibley Sympathatic fibers orignates from gonglion cells Digestive Processes) that reside in plexus at the base SMA. Enteric nervous systkin Consist of meissner plexus at bose of submucosa and Auerbach plexus between inner circumferential & outer longitudoval layers af muscle wall Pancreas Duodenum Extends from pylorus to duodenojejunal junction or to ligament of Treiz plica circulares: transverse mucosal folds in the lumen of small Intestine most prominent in proximal small bowel (duodenum, jejunum) than in Distal small intestine (ileum) Duodenum consists of 4 parts ① Superior (first) Part: duodenal bulb, 5 cm long, right side of most ileums ② Descending (second) part: 7-10 cm, curves around head of pancreas. ③ transverse (third) part: 6 cm, crosses anterior to aorta & IVC. Posterior to SMA's & superior mesenteric vein ④ Ascending (fourth) Part: 5 cm, ascents past left side of aorta & curves anteriorly to meet jejunum forming duodenojejunal junction which suspended by ligament of Treiz Blood supply up to ampulla of Vater → gastroduodenal artery beyond ampulla of Vater → inferior pancreaticoduodenal artery (branch of SMA) Venous Drainage → anterior & posterior pancreaticoduodenal vein drain into SMV (which joins splenic vein behind the neck of pancreas to form the portal vein) prepyloric vein of Mayo: landmark of pylorus jejunum and ileum No anatomical boundaries between the two. Imp long vasa rectae longer plica circulares thicker wall Imp shorter vasa rectae smaller plica circulans thinner wall Site of absorption of bile salts & B12, FA (terminal ileum) Blood supply → branches of SMA and Drain → SMV Large intestine Embryology: Mid Gut - up to transverse colon + small intestine except proximal duodenum Hind Gut - rest of colon & proximal anus Ectoderm - distal anus Transition between hind gut & ectoderm - dentate line Anatomy: 3-5 ft in length Colon Hepatic flexure Splenic flexure Cecum is the widest part then colon gets narrower distally 3 special structures: haustra, epiploic appendages, appendix Taenia coli: three distinct bands of longitudinal muscles converge at appendix and spread out to form longitudinal muscle layer at proximal rectum. Ascending colon Descending colon Sigmoid colon Cecum Appendix Rectum Epiploic appendages: fat appendages that hang off antimesenteric side of colon. Posterior to hepatic & splenic flexure. Retroperitoneal - ascending colon, descending colon Intraperitoneal - cecum, transverse colon, sigmoid colon No tenia in esophagus, middle and distal rectum Lines of toldt - lateral peritoneal reflection of ascending & descending colon Blood supply: SMA (mid colic - rt colic - ile colic) IMV (left colic - st colic - sigmoid arteries) Watershed area: (Poor blood supply) Splenic flexure rectosigmoid junction LN mostly follow arterial supply Innervation: Autonomic nervous system Sympathetic Parasympathetic Histology: Mucosa, submucosa, inner circular muscle layer, outer longitudinal muscle (teniae coli) (smooth muscle) Serosa Propria Microbiology: Sterile at birth, then normal flora established 49% anaerobic (mc Bacteroides fragilis) 11% aerobic (mc E.coli) LN: Ecolic LN Paracolic LN Para aortic LN Central LN Intermediate LN Rectum & Anus Rectum 12-15 cm in length. Can store up to 500 cc of feces Rectum has distinct peritoneal Covering. Hesto mucosa submuccisa mnes circuler outer longitud Waldeyer’s facia (Confluent) Rectal valve of Huston Anal canal From recal muscle Hemorrhoidal veins Not preserd in Disted & middle rechem Rectosacral facsa from sy vertebra body to reclam External anal sphincter Denovillers face= anal vorge crypt andocian to lower theid of rection Anal sinuses Anal canal beloven anederen & skin Pelvic floor levator ani (Pubococcygeus-iliococcygeus - Puboredalis muscle) by sa innenvale -Supplat by MA broach is superior secala (superis part) Internal iliac multe is Oistal rectus) για Rectum has 2 major angles play significant role of Continence red cocked at the origin of rectum at sacried promentery as it bends posterically & inferiaily Following Curve of the sacrum •canorectal angle: feromed by puborectalis muscle as it jon anus at pulling reckum fesward. Valba maneuver enhance these angles, closing of rectam Anus runs From verge to Dentale link ( anoderm and ferianal skin) From pelor, duphragm to anal verge (junction of anaknical anal coral *Dentale line line mucoculonas mu line smooth anoderm 1-150 Paive diam that seperate proximal mucosal from distal abere Dentale line Columinar epithelium below squamous epithelium. above anal endoderm Colums of margagni: 12-14 colum’s of plated macosa superior to dentale 1 verge Anoderm line, spealed by crypts Perianal gland discharge their secreation at the base of the columes Internal @imf anal sphider imp G -Consist of specialized reckel smarth muscles (from inner cisculer layer) External *Consist of, 3 loops of Voluntary striated muscle -Continuation of puborectatis muscle *Involuntary, 80% of contraction of rest 20% of resting pressure *100% of voluntary pressure supplied by Internal inform pudendal Con be classifed to Deep Supactical sabquntnous *hokkgy Anoderm LN: above dentale line Inferior mesenteric nude 7 Ingured nodes. os internal lloc node Physiology of colon & rectum main function absorption of water & electrolyte from stool storage of feces Motility (3 types of movement) Retrograde movement from transverse colon to cecum Segmental Contractions MC localized simultaneous contraction of longitudinal and circular muscles prolonging their exposure to absorptive epithelium Mass movement contraction of long segments of colon occur 3-4 times each day (especially after waking up or after eating & may result in bowel movement) 30 seconds in duration result in antegrade propulsion of luminal content at rate 0.5-1 cm/sec Neural Control External Para/sympathetic Internal mucosa, submucosal (Meissner's plexus), circular muscle layer by myenteric (Auerbach's) plexus, longitudinal muscle layer, subserosal plexus, visceral Defecation: mass movement causes feces to move into rectal vault Sampling reflex & Rectal Distention leading to involuntary relaxation of internal sphincter allowing descend of rectal contents and sensation of feces at transitional zone Voluntary relaxation of external sphincter pushes content down anal canal Voluntary increase in intraabdominal pressure assists in propelling rectal content out of anus Flatus: Voluntary Contractions of pelvic floor muscle causing selective passage of gas with retention of Stool