lecture 4 Anatomy of Digestive System.pptx
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Anatomy of Digestive System (part 2) Instructor : Dr. Abdulhafeed S. Dalab PhD in Anatomy and Cell Biology Department of Veterinary Medicine Faculty of Agriculture and Veterinary Medicine June, 2021 Pharynx 03/05/2024 2 Pharynx The common passageway for the digestive and respiratory system ...
Anatomy of Digestive System (part 2) Instructor : Dr. Abdulhafeed S. Dalab PhD in Anatomy and Cell Biology Department of Veterinary Medicine Faculty of Agriculture and Veterinary Medicine June, 2021 Pharynx 03/05/2024 2 Pharynx The common passageway for the digestive and respiratory system It connects the oral cavity with esophagus and nasal cavity with larynx The soft palate divides the rostral portion of pharynx into dorsal and ventral portion : Dorsal nasopharynx Part of respiratory channel extend from caudal nares to laryngopharynx Ventral oropharynx Part of digestive channel extend from oral cavity to the base of epiglottis The tow portion meet in intrapharyngeal opening The laryngopharynx extend from intrapharyngeal opining to the entrance of the esophagus and larynx 3 Openings of the pharynx Pharyngeal opening Opening from oral cavity to oropharynx Caudal nares (choanae) Osseous opening between caudal nasal cavity and nasopharynx Pharyngeal opening of auditory tube Slits in the lateral walls of nasopharynx leading to auditory tube Laryngeal opening Opining into larynx Esophageal opening 03/05/2024 Opening at the caudal end of the laryngopharynx into esophagus 4 03/05/2024 5 Pharynx In horse : the soft palate is extremely long, it lies ventrally and in front of the tip of epiglottis. So the horse unable to voluntarily raise its soft palate, it exclusively breathes through their nose. This explains why horses vomits through their nose 03/05/2024 6 03/05/2024 7 Cranial part of the alimentary canal Esophagus and stomach 03/05/2024 8 Esophagus 03/05/2024 9 Esophagus Tube between the pharynx and the stomach Begins dorsal to the cricoid cartilage of larynx and ends at the cardia of the stomach At its origin it passes dorsal to the trachea At thoracic inlet it comes to lie on the left lateral aspect of the trachea Within the thoracic cavity it is located dorsal to the trachea, over tracheal bifurcation. Within the abdominal cavity it is located at the dorsal border of the liver to join stomach at the cardia 03/05/2024 10 Esophagus Begins dorsal to the cricoid cartilage of larynx and ends at the cardia of the stomach At its origin it passes dorsal to the trachea 03/05/2024 11 Esophagus At thoracic inlet it comes to lie on the left lateral aspect of the trachea 03/05/2024 12 Esophagus Within the thoracic cavity it is located dorsal to the trachea, over tracheal bifurcation. 03/05/2024 13 Esophagus Within the abdominal cavity it is located at the dorsal border of the liver to join stomach at the cardia 03/05/2024 14 Esophagus Since it traverses most of the neck, all of thorax and ends on entering the abdomen, it is divided into Cervical part Thoracic part Abdominal part In ruminant and horse : the lumen of the esophagus narrows at the thoracic inlet and esophageal hiatus of diaphragm Predisposes this species to choke at those sites In carnivores : they are prone to mega- esophagus or dilatation of esophagus before it enters the abdomen 03/05/2024 15 Stomach 03/05/2024 16 Stomach (gastric or ventriculus) It is a large dilatation of the alimentary canal, caudal to the diaphragm located between the esophagus and duodenum. 03/05/2024 17 Classification of the stomach 1. According to the external shape and size or according to the number of cavities (Monolocular stomach) (Multilocular stomach) 2. According to the mucous membrane lining Simple stomach Compound stomach 03/05/2024 18 Classification of the stomach According to the external shape and size or according to the number of cavities: Monolocular stomach:- it is containing one cavity in (dog, horse, pig) all animals except ruminants. Multilocular stomach:- it is containing many cavities, in ruminants (ox, sheep and goat). 03/05/2024 19 Classification of the stomach Multilocular stomach 03/05/2024 Monolocular stomach 20 Classification of the stomach According to the mucous membrane lining: Stomachs are line by glandular epithelium, and non glandular epithelium or both. Simple stomach: is lined by one kind of mucosa (glandular mucosa) that covered by simple columnar epithelium, in dog, cat and man. Compound stomach: is lined by glandular (simple columnar epithelium), and non glandular mucosa (is a continuation of stratified squamous epithelium of esophagus) in horse, ruminants and pigs. 03/05/2024 21 Classification of the stomach In horse: the non- glandular region extends for a distance and then its transform to glandular region, these two regions are separated by an irregular folded edge of mucous membrane called Margo plicatus. In ruminants: the proximal three compartment (rumen, reticulum and omasum) are non-glandular therefore are called forestomach or proventriculus, the distal compartment (abomasum) is glandular portion similar to the simple stomach of other species, therefore is called true stomach. 03/05/2024 22 03/05/2024 23 03/05/2024 Horse stomach 24 Parts of simple stomach The form of the simple stomach is a J shape curved sac, which composed of: 1- Greater curvature: the long convex surface of the stomach extending from the cardia to the pylorus, it’s the attachment site of the greater omentum. 2- Lesser curvature: the short concave surface of the stomach also extending from the cardia to the pylorus, it’s the attachment of the caudal edge of the lesser omentum. 03/05/2024 25 Parts of simple stomach 3- Cardia: it consist of the cardiac opening (the opening between esophagus and stomach and consists of bundles of circular smooth muscle fibers). -fixed part of stomach 4- Fundus: is a blind expanded portion of the stomach on the left side adjacent to the cardia ( blind sac- homologus to forestomach in ruminant)). 5- Body: is the largest part of the stomach extending from cardia to the pylorus. 6- Pylorus: is the distal opening of the stomach surrounded by a strong band of circular smooth muscle fiber (pyloric sphnicter) through which the stomach contains are emptied into the duodenum. 26 Lesser curvature Greater curvature 03/05/2024 27 Gastric glands The stomach can be divided into 3 regions based on specific distribution of different type of gastric glands Region of cardiac glands Secret mucus for protection Region of fundic (gastric) glands Neck cells produce mucus Chief cells produce pepsinogen Parrietal cells produce chloride and hydrogen Region of pyloric glands 03/05/2024 28 03/05/2024 29 03/05/2024 30 Species differences Dog: the stomach is C- shaped , the cardia is wide, which may be related to the ease with the dogs vomit, in addition to gastric volvulus is relatively common, especially in large breeds Cat : the stomach is C-shaped but has narrower lumen than the dog, the angular notch is deep, make it difficult during endoscopy 03/05/2024 31 03/05/2024 32 Species differences In horse: the stomach is small, its capacity is between 5-15 L, which has to taken into account when administration of nasogastric tube to avoid over distension Blind sac (saccus caecus) : extensive fundus lined by non glandular mucosa homologues to forestomach of ruminant In some horses non-glandular regions is marked by scars from larvae of gastrophilus. The cardiac sphincter is especially well developed and this , together with the oblique entrance of esophagus , is thought to be responsible for the reputed inability to vomit 03/05/2024 33 03/05/2024 34 Compound stomach The stomach of domestic ruminants is composed of four chambers: Rumen Reticulum Omasum Abomasum Rumen, Reticulum, Omasum are referred to as forestomach (proventriculus) Non-glandular mucosa Responsible for the enzymatic destruction of carbohydrates (cellulose) with the help of microbes The last chamber, the abomasum, has a glandular mucosa and is comparable to simple stomach of horse and dog. 03/05/2024 35 03/05/2024 Rumen: lies on the left. Reticulum: lies on the cranial. Omasum: lies on the right. Abomasum: lies ventrally. 36 Rumen Is a large laterally compressed sac it extends from the diaphragm to the pelvic inlet, filling the left half of the abdominal cavity. The rumen is divided into several portions by inflections of the walls called the pillars of rumen that project into the lumen: 03/05/2024 Ventral sac Dorsal sac Cranial sac (atrium ) Caudodorsal blind sac Caudoventral blind sac 37 Rumen 03/05/2024 38 03/05/2024 39 03/05/2024 40 Rumen 03/05/2024 41 Rumen The non- glandular mucosa of rumen consist of papillae (ruminal papillae) To increase surface area 7 fold Important in reabsorption of volatile fatty acids Reabsorption of water, vitamins K and B Short or long size of this papillae is depending on 03/05/2024 Animal diet Seasoms 42 03/05/2024 43 Openings of the rumen Cardiac orifice: is the opening of the esophagus into the stomach. Rumeno-reticular orifice : is the opening which communicate the cranial sac with the reticulum. 03/05/2024 44 Reticulum Is the most cranial compartment of the ruminal stomach. Lies between the diaphragm and the rumen. The non-glandular mucosa of the reticulum forms permanent crest, which intersect to form honey comb like cells. each cell is divided by a secondary crests (ridge) and both the cell and the crest are studded with small papillae. 03/05/2024 45 Reticulum 03/05/2024 46 03/05/2024 47 Omasum Round organ located chiefly to the right of the median plane. Communicates with reticulum through the reticulo-omasal opening and with abomasums through the omaso-abomasal opening. omaso-abomasal opening: flanked by 2 mucosal folds to prevent reflux of ingesta from abomasum into omasum. The omasum is larger than the reticulum in ox, and smaller than the reticulum in sheep and goats. Arising from the wall parallel folds of varying sizes called omasal laminae (They are thin muscular sheet). For water reabsobtion 03/05/2024 48 Omasum 03/05/2024 49 03/05/2024 50 Omasum 03/05/2024 51 Omasum These laminae are covered by short papillae. Between the laminae are the interlaminar recesses. 03/05/2024 52 Abomasum It is an elongated sac. It can be divided into fundus, body and pylorus (simple stomach) lies chiefly in the floor of the abdominal cavity The abomasum is lined with glandular mucosa. Gastric glands Pyloric glands The mucosa is arranged in large permanent spiral folds (10 to 17). The pyloric sphincter is not very well developed in ruminants, however, a large torus pyloricus is present. 03/05/2024 53 Abomasum 03/05/2024 54 03/05/2024 55 Abomasum 03/05/2024 56 Gastric groove Channel through stomach in suckling ruminants. The gastric groove is divided into : Reticular groove Omasal groove Abomasal groove Suckling with head up causes lips of this groove to close, this form a tube from the cardiac opening to the abomasum through this tube, milk bypasses the rumen , reticulum and omasum to empty directly into the abomasum 03/05/2024 57 Gastric groove 03/05/2024 58 Blood of the simple stomach (horse) The stomach is supply by celiac artery which arises from the ventral aspect of the abdominal aorta, it divided in to three main branches: Left gastric artery. Hepatic artery. Splenic artery. 03/05/2024 59 Blood supply of the compound stomach Right ruminal artery. Left ruminal artery. 03/05/2024 60
