GIT lec PDF

Digestive System= Gastrointestinal tract (GIT) and associated glands The di gesti ve sy stem c onsi sts of the mouth, the phar y nx, the oesopha gu s, the stomac h, the small i ntesti ne and the lar ge i ntesti ne. I t also i nc ludes the assoc i ated glands as the sali var y glands, the li ver, an...

Digestive System= Gastrointestinal tract (GIT) and associated glands The di gesti ve sy stem c onsi sts of the mouth, the phar y nx, the oesopha gu s, the stomac h, the small i ntesti ne and the lar ge i ntesti ne. I t also i nc ludes the assoc i ated glands as the sali var y glands, the li ver, and the panc r eas.  Identify The different parts of GIT By the end of this lecture Describe The associated glands you’ll be able to: Define Biliary system  The mouth is the first part of the GIT. The mouth is composed of a smaller outer part called the vestibule and a larger inner part called the mouth cavity proper. The vestibule is bounded externally by the cheeks and lips and internally by the teeth and gums. The opening between the lips is called the oral fissure. The mouth cavity proper is bounded anteriorly and on each side by the teeth and gums. Posteriorly it communicates with the oropharynx. The roof is formed by the hard and soft palates which separate it from the nasal cavity. The floor of the mouth is principally formed by the tongue and the sublingual salivary glands, which raise a ridge of mucous membrane called the sublingual fold.  T he o e so pha gus i s a musc ul a r t ube a bout 25 c m in le ngt h. It e xt e nds fro m t he l o we r e nd o f t he pha rynx t o t he c a rdi a c o ri fi c e o f t he st o ma c h. It pa sse s i n t he ne c k ( c e rvi c a l pa rt ) , in t he t hora x ( t hora c ic pa rt ) , a nd in t he a bdo me n ( a bdo mi na l pa rt ). It t ra nsmi t s t he fo o d fro m t he pha rynx t o t he st o ma c h.  It is the most distensible portion of the alimentary tract. It transmits food from the oesophagus to the duodenum. It lies in the upper left part of the abdominal cavity below the diaphragm. It has two openings; the cardiac orifice lying at the junction with the oesophagus and the pyloric orifice (pylorus) at the junction of the stomach with the duodenum; it is guarded by a thick pyloric sphincter It has two surfaces; anterior and posterior, and two borders called the lesser and the greater curvatures. The lesser curvature is the concave right border while the greater curvature is the larger (4 times larger) convex left border. The stomach can hold up to 3 liters of material in the adult. In the newborn, the stomach is about the size of the hen's egg, and it can hold about 30 ml of fluid. The stomach functions as a reservoir for food and it secretes the digestive juice which contains hydrochloric acid and certain enzymes  The small intestine extends from the pylorus of the stomach to the ileocaecal junction where it joins the large intestine. It is about 6 meters (20 feet) long and it is divided into three parts; duodenum, jejunum, and ileum. The jejunum and ileum are connected to the posterior abdominal wall by a peritoneal fold called the mesentery. A. The duodenum: ‫االثنى عشر‬ Pancreas It is 25 cm (10 inches) long. It lies on Pancreatic duct the posterior abdominal. It is C-shaped and it surrounds the head of the pancreas. The bile duct and the pancreatic duct unite and open by a common opening Bile duct into of the middle of the duodenum. B. The jejunum: ‫الصائمي‬ It is called so because it contains no food after death. It comprises the upper 2/5 of the small intestine distal to the duodenum. C. The ileum: ‫اللفائفي‬ It is called so because it is the most coiled part of the small intestine. It comprises the following 3/5 of the small intestine. Duodenum Head of Pancreas  DIffERENCES BETWEEN THE JEJUNUM AND ILEUM Jejunum ileum Larger in diameter Smaller in diameter The mesentery contains small The mesentry contains amount of fat so it is easy to much of fat obscuring its see its blood vessels blood vessels The circular folds of the The circular folds and villi mucosa and the villi are of the mucosa are smaller larger and more numerous and less numerous. Mucosa contains few small Mucosa contains large lymphoid follicles aggregations of lymphoid Function of the small intestine: follicles = Peyer’s patches The upper part of small intestine is mainly digestive, while its lower part is mainly absorptive.  The large intestine extends from the ileocaecal junction to the anus. it is about 1.5 meters long. It consists of the caecum and vermiform appendix, the ascending colon, the right colic flexure (hepatic flexure), the transverse colon, the left colic flexure (splenic flexure), the pelvic colon, the rectum and anal canal.  The caecum The vermiform appendix: The caecum is present in the right iliac A very narrow worm-like tube which fossa. It is 6 cm long. It is a blind pouch opens into the of the caecum about one which is continuous above with the inch (2.5 cm) below the ileocaecal ascending colon. junction. The ileum opens into the large Its average length is 9 cm. It usually intestine at the junction between the lies behind the caecum (retrocaecal) or caecum and ascending colon. The extending into the pelvis (pelvic). vermiform appendix opens into the posteromedial aspect of the caecum about one inch (2.5 cm) below the ileocaecal junction. Ileum Vermiform appendix  The pelvic (sigmoid) colon: It is about 40 cm in length. It begins at the inlet of the pelvis and ends at the middle of the sacrum where it is connected with the The descending colon: rectum. It is about 25 cm in It forms a loop, and it is length. It extends from surrounded by a peritoneal fold the splenic flexure to end called pelvic mesocolon, so it at the inlet of the is freely movable and hangs in the pelvis where it joins the pelvic cavity. pelvic colon.  Rt Lt The rectum: It is about 12 cm in length. It begins at the middle of the sacrum and ends below the coccyx where it opens into the anal canal. In human, it is not straight as its name implies but it rather forms 3 flexures two to the right and one to the left. 3 Flexures The anal canal: It is about 4 cm in length and ends below in the perineum by anal opening (anus). Internal and external sphincters control the opening. Rectum & anal canal Anterior view  Differences between the large and small intestine. Large intestine Small intestine Larger in diameter Smaller in diameter It is 1.5 meters in length It is 6 meters in length The external surface The external surface contains appendices does not contain epiploicae appendices epiploicae The longitudinal muscle layer forms 3 longitudinal bands called The longitudinal muscle taeniae coli layer does not form which are shorter in bands and the wall of length than the true the small intestine is length of the large smooth without intestine so that the wall haustrations. presents haustrations Part of the large intestine (sacculations). The peritoneum: It is a serous membrane formed of two layers; a parietal layer lining the wall of the abdomen, and a visceral layer covering the abdominal viscera. In some regions It extends as a fold formed of 2 layers to connect the internal organs with the abdominal wall, e.g., the mesentery and the transverse mesocolon, so that it facilitates the movement of organs of alimentary canal. mesocolon mesentery The three glands 1- Salivary Glands associated with 2- Liver the alimentary 3- Pancreas canal The salivary glands Ther e ar e t hr ee pair s of salivar y glands, w hich secr et e t he saliva int o t he mout h. glands paro tid gland sublingual gland submandibular gland The parotid glands located one on each sid e in front and below the external ear. Each g land has a duct that op ens in the v estib ule of the mouth op p osite the up p er 2 nd molar tooth. The submandibular glands Located b el ow th e b od y of th e man d ib l e n ear its an g l e. Th eir d u cts op en u n d er th e ton g u e. The sublingual glands loc at ed dir ec t ly under t he t ongue, c over ed by t he muc ous membr ane of t he f loor of t he mout h, r ais ing t he t w o s ublingual f olds. They open by numer ous s hor t duc t s ( 8- 20) in t he f loor of t he mout h. 2- Pancreas The p anc r eas ex tend s tr ansv er sely on the p oster ior ab d ominal wall in fr ont of the up p er two lumb ar Spleen ver teb r ae. It is 15 c m in leng th. Its ex p and ed r ig ht p ar t is c alled the head and it Tail is sur r ound ed b y the d uod enum. The head is followed b y a c onstr ic ted p ar t c alled the neck. The Neck Body nec k is followed b y the main p ar t c alled the bo dy. The left tap er ing end of the p anc r eas is the c alled the tail whic h r ests on the sp leen. Head The p anc r eas ser ves b oth ex oc r ine and end oc r ine func tions. It sec r etes the p anc r eatic juic e and the hor mone, insulin. The d uc t of the p anc r eas whic h tr ansmits the p anc r eatic juic e, op ens with the c ommon b ile d uc t in the mid d le of the d uod enum. 3- The liver Th e l iver is a l arg e g l an d weig h ing over 1.5 kg. It is wed g e sh ap ed with its b ase d irected to th e righ t and its ap ex d irected to th e l eft. It l ies in the up p er rig ht side of the abdominal cav ity just under the diaphragm. It is d ivid ed in to two main l ob es; a l arg e rig h t l ob e an d a smal l er l eft l ob e. A smal l er p art; th e quadrate l ob e, is d emarcated on th e in ferior su rface of th e rig h t l ob e an d an oth er circu mscrib ed p art on its p osterior su rface is cal l ed th e caudate l ob e. Th e porta hepatis is an op en in g on its in ferior su rface b eh in d th e q u ad rate l ob e th rou g h wh ich th e rig h t an d l eft h ep atic d u cts, th e h ep atic artery an d th e p ortal vein p ass in th at ord er from b efore b ackward s.  Blood supply of the liver: T he liver has a dual blo o d supply: a) O xygenated blo o d f o r m the h epatic artery whic h ar ises fo r m the c o eliac tr unk ; a br anc h fr o m the ao r ta. b) Po r tal veno us blo o d f r o m the portal vein. T he blo o d leaves the liver thr o ugh the h epatic vein s to the infer io r vena c ava. T he liver is the site o f ver y many vital metabo lic pr o c esses. It also sec r etes bile.  I t c o ns i s t s o f t he duc t s t hro u g h w hi c h t he bi le i s The biliary system t ra ns po rt e d a n d t he ga l l bla d de r, w hi c h c o nc e nt ra t e s it. The ga ll b ladd er : I t i s a pe a r-s ha pe d o rga n (7 -1 0 c m i n le n gt h) ha v i n g a c a pa c i t y o f 3 0 -5 0 ml. i t i s a t t a c he d t o t he i nf e ri o r s urf a c e o f t he li v e r o n t he ri g ht s i de o f t he qua dra t e lo be. T h e rig h t a n d le ft h e p a t ic d u c ts , le a v e t he li v e r t hro ug h t he po rt a he pa t i s and u ni t e to f o r m t he c o m m o n h e p a tic d u c t (3 c m i n le n gt h). T he c o mmo n he pa t i c duc t u ni t e s wi t h t he c ys t ic d u c t (3 -4 c m i n le n gt h) f ro m t he ga l l b la d de r t o f o r m t he c o m m o n b i le d u c t (7. 5 c m i n le n gt h). T h e c o m m o n b i le d u c t o p e n s to g e th e r wi th th e p a n c re a ti c d u c t i n th e m i d d l e o f th e d u o d e n u m. 1-The vestibule of the mouth contains the opening of: A. Parotid d uct B. Sub mand ib ular d uct C. Sub ling ual d uct D. Cy stic d uct E. Hep atic d uct 2- A 36- y ear - o ld w o m an is ho s pitalized fo r treatm ent o f a s to m ach ulcer that has been getting pro gres s iv ely w o rs e o v er s ev eral m o nths. R adio graphic s tudies rev eal the s ite o f inv o lv em ent to be alo ng the greater curv ature, appro xim ately 4 cm aw ay fro m the py lo ric s phincter. Py lo ric s phincter leads to : A. Esop hag us B. Duod enum C. Jejunum D. Ileum E. Lesser curv ature 3- What is the name of the muscular ring that separates the stomach from the small intestine? A. Py loric sp hincter B. Ileocaecal valve C. Sig moid colon D. Anal sp hincter E. Duod enal p ap illa 4- What is the name of the last part of the large intestine? A. Jejunum B. Ileum C. Duod enum D. Colon E. Anal canal References p. 111 – 115 Q1 → A Q2 → B Q3 → A Q4 → E Thank You