Digestive system

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1. Digestive System By Dr. Vibhash Kumar Vaidya

2. Digestive System The digestive system consists of digestive tract and associated organs of digestion. It provides water, electrolytes, vitamins and nutrients to the body with the help of the circulatory system.

3. The functions of digestive system are:- Ingestion : taking in food through mouth. Mastication : movements of the lower jaw during chewing. Deglutition : swallowing of food so that it passes from mouth to stomach. Digestion : chemical breakdown of food material. Absorption : nutrient molecules absorbed into circulatory system through mucous membrane of small intestine. Defecation : elimination of solid/semisolid/liquid waste material of food through anus.

4. Digestive tract The digestive tract extends from the mouth to the anus. It is tubular passage and measures about 10 m (30 ft ) in length. Proximal to distal GIT consists of following parsts : Mouth Pharynx Esophagus Stomach Small intestine Large intestine Rectum Anal canal

5. Mouth (oral cavity) It is the first part of the digestive tract. It bounded anteriorly by lips, laterally by cheeks, superiorly by palate and inferiorly by a muscular floor. Teeth The teeth are embedded in the sockets of alveolar process of mandible and maxilla. In adult individual, there are 32 teeth, 16 in each jaw.

6. TONGUE The tongue is a mobile muscular organ in the oral cavity, which bulges upwards from the floor of the mouth. It is a mass of skeletal muscle covered by mucus membrane. The muscle mass is separated into right and left halves by a midline fibrous septum. The tongue is separated from teeth by a deep alveololingual sulcus.

7. Functions The tongue are : 1. Taste. 2. Speech. 3. Mastication. 4. Deglutition. Shape The tongue is conical in shape. External Features of The tongue: 1. A root. 2. A tip. 3. A body.

8. Muscles of the Tongue The musculature of tongue consists of extrinsic and intrinsic muscles . The intrinsic muscles are within the tongue and have no attachment outside the tongue. whereas extrinsic muscles take origin from outside the tongue and enter the tongue to be inserted. The intrinsic muscles change the shape of tongue whereas extrinsic muscles move the tongue (such as protrusion, retraction and side-to-side movements) as well as alter its shape.

9. Intrinsic muscles Superior longitudinal. Inferior longitudinal. Transverse. Vertical . Extrinsic muscles Genioglossus . Hyoglossus . Styloglossus . Palatoglossus .

10. Arterial Supply 1. Branches of lingual artery (chief artery of tongue). 2 . Tonsillar branch of the facial artery. 3 . Ascending pharyngeal artery . Venous Drainage: 1 . Deep lingual vein Nerve Supply: Motor supply: All the muscles of tongue (intrinsic and extrinsic) are supplied by the hypoglossal nerve except palatoglossus which is supplied by cranial root of accessory via pharyngeal plexus. Sensory supply: Anterior 2/3 of the tongue is supplied by : ( a) lingual nerve carrying general sensations , (b ) chorda tympani nerve carrying special sensations of taste. Posterior 1/3 of the tongue is supplied by : glossopharyngeal nerve, carrying both general and special sensations of taste. P osteriormost part (base of the tongue), supplied by the internal laryngeal branch of the superior laryngeal carrying special sensations of taste.

11. PHARYNX The pharynx is a funnel-shaped fibromuscular tube. extending from the base of the skull to the esophagus. It is lined throughout with mucous membrane. The pharynx acts as a common channel for both food (deglutition) and air (respiration). MEASUREMENTS Length : 12–14 cm, Width : 3.5 cm at its base, and 1.5 cm at pharyngoesophageal junction.

12. ESOPHAGUS The esophagus is a narrow muscular tube extending from pharynx to the stomach. It is about 25 cm long and provides passage for chewed food (bolus) and liquids during the third stage of deglutition. The anatomy of esophagus is clinically important because of its involvement in various diseases such as esophagitis, esophageal varices and cancer. It begins with lower part of the neck and terminates in the upper part of the abdomen by joining the upper end of the stomach.

13. PARTS OF THE ESOPHAGUS Cervical part (4 cm in length ). Thoracic part (20 cm in length ). Abdominal part (1–2 cm in length).

14. CONSTRICTIONS Normally, there are four sites of anatomical constrictions/ narrowings in the esophagus. The distance of each constriction is measured from the upper incisor teeth . 1. First constriction, at the pharyngo -esophageal junction, 9 cm (6 inches) from the incisor teeth. 2 . Second constriction, where it is crossed by the arch of aorta, 22.5 cm (9 inches) from the incisor teeth. 3 . Third constriction, where it is crossed by the left principal bronchus, 27.5 cm (11 inches) from the incisor teeth. 4 . Fourth constriction, where it pierces the diaphragm, 40 cm (15 inches) from the incisor teeth.

15. STOMACH The stomach is the widest and most distensible part of the alimentary canal between the esophagus and the duodenum. The main functions of stomach are: 1 . Forms a reservoir of food. 2 . Mixes food with gastric secretions to form a semifluid substance called chyme . 3.Hydrochloric acid secreted by the gastric glands destroys bacteria present in the food and drink.

16. Shape : The stomach is mostly “J” shaped . Size and Capacity Length: 10 inches. Capacity : The capacity of the stomach is variable as the stomach is highly distensible: 1 . At birth the capacity is only 30 ml (1 ounce ). 2 . At puberty the capacity is 1000 ml (1 L ). 3 . In adults the capacity is 1500 to 2000 ml.

17. EXTERNAL FEATURES 1. Two ends : Cardiac and pyloric. 2 . Two curvatures : Greater and lesser. 3 . Two surfaces : Anterior ( anterosuperior ) and posterior ( posteroinferior ).

18. PARTS The stomach has four parts: 1. Cardiac part (or cardia ). 2 . Fundus. 3 . Body. 4 . Pyloric part.

19. Visceral Relations 1 . Relations of the anterior ( anterosuperior ) surface: ( a) On the right side this surface is related to the gastric impression of the left lobe of the liver and near the pylorus to the quadrate lobe of the liver . ( b) The left half of this surface is related to the diaphragm and rib cage . ( c) The lower part of this surface is related to the anterior abdominal wall.

20. Relations of the posterior ( posteroinferior ) surface: This surface is related to a number of structures on the posterior abdominal wall, which collectively form the stomach bed. These structures are : ( a) Diaphragm . ( b) Left kidney . ( c) Left suprarenal gland . ( d) Pancreas . ( e) Transverse mesocolon . ( f) Left colic flexure (splenic flexure of colon ). ( g) Splenic artery. (h) Spleen.

21. ARTERIAL SUPPLY The stomach has rich arterial supply derived from the coeliac trunk and its branches. 1 . Left gastric artery, a direct branch from the coeliac trunk. 2 . Right gastric artery, a branch of the common hepatic artery. 3 . Left gastroepiploic artery, a branch of the splenic artery. 4 . Right gastroepiploic artery, a branch of the gastroduodenal artery. 5 . Short gastric arteries (five to seven in number), branches of the splenic artery.

22. VENOUS DRAINAGE The veins of the stomach correspond to the arteries and drain directly or indirectly into the portal vein. 1 . Left gastric vein. 2 . Right gastric vein. 3 . Left gastroepiploic vein. 4 . Right gastroepiploic vein. 5 . Short gastric veins . NERVE SUPLLY The stomach has both sympathetic and parasympathetic innervation. Sympathetic Innervation The sympathetic fibres are derived from T6 to T10 spinal segments via greater splanchnic nerves, and coeliac and hepatic plexuses. Parasympathetic Innervation The parasympathetic fibres are derived directly from the vagus nerves.

23. DUODENUM The duodenum is the first, shortest, widest, and the most fixed part of the small intestine. It extends from the pylorus to the duodenojejunal flexure. It was so named by Herophilus in 300 BC because its length was approximately equal to the combined width of 12 fingers. The duodenum is 10 inches (25 cm) long. It receives chyme from the stomach which is mixed with bile and pancreatic enzymes here.

24. SHAPE & PARTS The duodenum is a “C”-shaped loop of the small intestine. The concavity of the duodenal loop encloses the head of pancreas. For descriptive purposes, the 25 cm long duodenum is divided into four parts: 1 . Superior (first) part, 5 cm (2 inches) long. 2. Descending (second) part, 7.5 cm (3 inches) long. 3 . Horizontal (third) part, 10 cm (4 inches) long. 4 . Ascending (fourth) part, 2.5 cm (1 inch) long .

25. Arterial Supply : 1 st part- branches from right gastric artery 2 nd part- up to the major duodenal papilla, by superior pancreaticoduodenal artery. Rest of the duodenum- inferior pancreaticoduodenal artery . Venous drainage : corresponding veins drain into superior mesenteric and portal veins. Nerve supply : ANS Sympathetic- T9- T10 segments Parasympathetic- Vagus

26. JEJUNUM AND ILEUM The small intestine proper extends from the duodenojejunal flexure to the ileocaecal junction. Its upper two-fifth forms the jejunum and its lower three-fifth forms the ileum. However , there is no definite line of demarcation. The jejunum and ileum are suspended from the posterior abdominal wall by a large fold of peritoneum called the mesentery of small intestine. The structure of the small intestine corresponds to its functional requirements.

27. Differences between the jejunum and ileum

28. Differences between the jejunum and ileum

29. ARTERIAL SUPPLY The jejunum and ileum are supplied by the jejunal and ileal branches (12–15 in number) of the superior mesenteric artery. DRAINAGE The veins correspond to the branches of superior mesenteric artery and drain into the portal vein, which carries the products of protein and carbohydrates to the liver . NERVE SUPPLY The small intestine is supplied by both sympathetic and parasympathetic nerve fibres .

30. LARGE INTESTINE The large intestine is about 1.5 m long and extends from the caecum in the right iliac fossa to the anus in the perineum. The functions of the large intestine are: 1 . Absorption of water from fluid contents in it to help form the feces. 2. Storage, lubrication, and expulsion of feces. 3 . Synthesis of vitamin B complex by normal bacterial flora present its lumen. 4 . Protection from invasion by microorganisms by its mucoid secretion which is rich in IgA group of antibodies.

31. PARTS For descriptive purposes, the large intestine is divided into the following four parts: 1 . Caecum and appendix. 2 . Colon. 3 . Rectum. 4 . Anal canal. The colon is further divided into four parts: ascending colon, transverse colon, descending colon, and sigmoid colon.

32. CARDINAL (DISTINGUISHING) FEATURES The three cardinal features of the large intestine are found: ( a) teniae coli . ( b) appendices epiploicae . (c ) sacculations (or haustrations ).

33. CAECUM The caecum (L. caecum = blind) is the large dilated blind sac at the commencement (proximal end) of the large intestine. It is situated in the right iliac fossa above the lateral half of the inguinal ligament. It communicates : ( a) Superiorly with the ascending colon . ( b) Medially at the ileocaecal junction with ileum, and posteromedially with appendix .

34. DIMENSIONS Length : 6 cm (2½ inches ). Width : 7.5 cm (3 inches ).

35. Types of Caecum On the basis of growth of the caecum later on, four types of caecum may be found in adults. 1 . Conical type/fetal type (2%): The caecum is conical and the appendix is attached at its apex. 2 . Infantile type (3%): The caecum is quadrate in shape (due to equal size of right and left saccules ) and the appendix is attached at the depressed bottom. 3 . Normal type (80–90%): The right saccule is larger than the left and the appendix is attached on the posteromedial aspect about 2 cm below the ileocaecal junction. 4 . Exaggerated type (4–5%): The right saccule is large (due to its exaggerated growth) and the left saccule is absent. The appendix is attached just below the ileocaecal junction.

36. Types of Caecum

37. BLOOD SUPPLY: anterior and posterior caecal branches of the ileocolic artery, a branch of superior mesenteric artery. The veins of the caecum follow the arteries and drain into the superior mesenteric vein, which finally drains into the portal system . NERVE SUPPLY The sympathetic nerve supply is derived from T11 and L1 spinal segments through superior mesenteric plexus. The parasympathetic nerve supply is derived from both vagus nerves.

38. VERMIFORM APPENDIX The vermiform appendix is a narrow worm-like diverticulum, which arise from the posteromedial wall of the caecum about 2 cm below the ileocaecal junction . DIMENSIONS The appendix varies in length from 2 to 20 cm (average 9 cm). The average width is about 5 mm. The diameter of lumen varies with age.

39. POSITIONS

40. COLON For descriptive purposes, the colon is divided into four parts: ( a) ascending colon. (b ) transverse colon. (c ) descending colon. (d ) sigmoid colon .

41. Ascending Colon : The ascending colon is an upward continuation of the caecum. It is about 5 inch (12.5 cm) in length and extends from the caecum, at the level of ileocaecal orifice, to the inferior surface of the right lobe of the liver where it bends to the left to form the hepatic (right colic) flexure . Transverse Colon : It is the longest (20 inch/50 cm in length) and most mobile part of the large intestine. It extends from the right colic flexure (in right lumbar region) to the left colic flexure (in the left hypochondriac region ).

42. Descending Colon : The descending colon is longer (25 cm), narrower, and more deeply located than the ascending colon. It extends from the left colic flexure to the front of the left external iliac artery at the level of pelvic brim where it becomes continuous with the pelvic colon ( sigmoid colon ). Sigmoid Colon (Pelvic Colon ) : The sigmoid colon is about 15 inches (37.5 cm) long and connects the descending colon with the rectum. It is S-shaped and hence its name, sigmoid colon. It extends from the lower end of descending colon at the left pelvic inlet to the pelvic surface of the third piece of sacrum, where it becomes continuous with the rectum.

43. ARTERIAL SUPPLY The colon is supplied by the following arteries: 1 . Ileocolic artery. 2 . Right colic artery. 3 . Middle colic artery. 4 . Left colic artery . VENOUS DRAINAGE 1. The veins draining the colon accompany the arteries

44. RECTUM The rectum is the distal part of the large intestine between the sigmoid colon and the anal canal. In Latin, the word “rectum” means straight; but the rectum is straight in quadrupeds and not in men. Although the rectum is a part of the large intestine, it is devoid of taenia coli, sacculations and appendices epiploicae —the cardinal features of the large intestine. The distension of the rectum initiates the desire to defecate.

45. Measurements The rectum is 5 inches (12 cm) long. The diameter of the rectum is not uniform throughout. In the upper part it is 4 cm as that of the sigmoid colon. In the lower part, it forms a dilatation called rectal ampulla

46. ANAL CANAL The anal canal is the terminal part (3.8 cm long) of the large intestine, situated in the perineum below the pelvic diaphragm. Like rectum it is devoid of sacculations , taenia coli, and appendices epiploicae . It is surrounded by an inner involuntary sphincter and an outer voluntary sphincter, whose tone keeps the anal canal closed except during the defecation.

47. EXTENT The anal canal begins at the anorectal junction, passes downward and backward, and opens at the anal orifice, which is situated in the natal cleft (cleft between the buttocks) about 4 cm below and in front of the tip of coccyx.

48. By. Dr Vibhash Kumar Vaidya Department of Anatomy LIVER

49. Introduction (Greek hepar : liver) It is the largest gland of the body. occupying much of the right upper part of the abdominal cavity . It consists of both exocrine and endocrine parts. The liver performs a wide range of metabolic activities necessary for homeostasis, nutrition, and immune response.

50. LOCATION The liver almost fully occupies: T he right hypochondrium. U pper part of the epigastrium. A nd part of the left hypochondrium up to the left lateral (midclavicular) line. It extends upward under the rib cage as far as the 5th rib anteriorly on the right side ( below the right nipple) and left 5th intercostal space

51. SHAPE, SIZE, AND COLOUR Shape The liver is wedge shaped and resembles a four-sided pyramid laid on one side with its base directed towards the right and apex directed towards the left . Colour It is red-brown in colour . Weight In males: 1.4 to 1.8kg. In females: 1.2 to 1.4kg. In newborn: 1/18th of the body weight. At birth: 150 g. Proportional weight: In adult 1/40th of the body weight.

52. EXTERNAL FEATURES The wedge-shaped liver presents: T wo well-defined surfaces: diaphragmatic and visceral. O ne well-defined border: inferior border .

53. Diaphragmatic Surface The dome-shaped diaphragmatic surface includes smooth peritoneal areas which face superiorly, anteriorly and to the right. And a rough bare area (devoid of the peritoneum) which faces posteriorly . The inferior vena cava (IVC) is embedded in the deep sulcus in the left part of the bare area. In most cases, this sulcus is roofed by the fibrous tissue termed ligament of IVC which may contain hepatic tissue converting the sulcus into the tunnel. The peritoneal ligaments are coronary, left and right triangular and falciform ligaments .

54. Visceral Surface (Inferior Surface ): R elatively flat or concave. It is directed downward , backward, and to the left. It is separated in front from the diaphragmatic surface by the sharp inferior border and behind from the diaphragm by the posterior layer of coronary ligament. The notable features on the visceral surface are: Fossa for the gallbladder. Fissure for the ligamentum teres hepatis. Porta hepatis. The visceral surface is covered by the peritoneum except at the fossa for gallbladder and the porta hepatis .

55. Inferior Border The features of the inferior border are as follows: It separates the diaphragmatic surface from the visceral surface . It is rounded laterally where it separates the right lateral surface from the inferior surface. It is thin and sharp medially where it separates the anterior surface from the inferior surface. It presents two notches: (a) Notch for ligamentum teres or interlobar notch: It is located just to the right of the median plane. (b) Cystic notch: It is located about 5 cm to the right of the median plane and often corresponds to the fundus of the gallbladder .

56. LOBES OF THE LIVER Anatomical Lobes: On the diaphragmatic surface: the liver is divided into two lobes , right and left, by the attachment of the falciform ligament. The right lobe which forms the base of the wedge-shaped liver is approximately six times larger than the left lobe .

57. On the visceral surface: the liver is divided into four lobes : Right lobe: to right of the fossa for gallbladder. Left lobe: to the left of the fissures for ligamentum teres and ligamentum venosum. Quadrate lobe: between the fossa for gallbladder and the fissure for ligamentum teres below the porta hepatis . Caudate lobe: between the groove for IVC and the fissure for ligamentum venosum.

58. Relations of diaphragmatic and visceral surfaces of the liver.

59. BLOOD SUPPLY The liver is a highly vascular organ. It receives blood from two sources . The arterial blood (oxygenated) is supplied by the hepatic artery and venous blood (rich in nutrients) is supplied by the portal vein. T hrough the liver. About 80% of this is delivered through the portal vein and 20% is delivered through the hepatic artery .

60. VENOUS DRAINAGE Most of the venous blood from liver is drained by three large hepatic veins: left hepatic vein between medial and lateral segments of the left true lobe, middle hepatic vein between true right and left true lobes, right hepatic vein between anterior and posterior segments of the right true lobe .

61. NERVE SUPPLY The liver is supplied by both sympathetic and parasympathetic fibres. The sympathetic fibres are derived from the coeliac plexus. The parasympathetic fibres are derived from the hepatic branch of the anterior vagal trunk .

62. GALL BLADDER The gallbladder is an elongated pear-shaped sac of about 30–50 ml capacity. It stores and concentrates the bile and discharges it into the duodenum by its muscular contraction.

63. Location : The gallbladder lies in the fossa for gallbladder on the inferior surface of the right lobe of the liver. Dimensions Length : 10 cm. Width: 3 cm (at its widest part). Parts and Relations : The gallbladder is divided into the following three parts: fundus , body, and neck.

64. Arterial Supply: The gallbladder is supplied by the cystic artery (a branch of right hepatic artery ). Venous Drainage: The venous drainage of the gallbladder by the cystic vein. Nerve supply: ANS