Stomach and Intestines
DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Stomach and Intestines CRT04101 · Anatomy, Physiology and Pathology START READING NOTES Study Stomach and Intestines using the sections below. Use the topic navigation to continue through Anatomy, Physiology and Pathology. Contents of This Topic Structure of the Pharynx and Oesophagus Stomach and Intestines The oesophagus has 4 constrictions where adjacent structure produce impression It has four layers; from outside: Structure and Functions of the Stomach The stomach: The most dilated part of the gastrointestinal tract Structure of the Stomach The stomach is lined with simple columnar epithelium Blood supply of the stomach; a rich arterial supply, arise from the celiac trunk and its branches. Functions of GIS Functions of the Stomach Structure and functions of the Small Intestines The small intestine extends from the pyloric sphincter to the ileocecal valve Duodenum is the first section of the small intestine The jejunum is the middle section of the small intestine The ileum is the final section of the small intestine There are, however, subtle differences between the two Structure and Functions of the Large Intestine The following are the parts of the large intestine: If defecation is delayed for a prolonged period, constipation and hardened faeces results The anus is an opening at the opposite end of the digestive tract from the mouth Key points evaluation Structure and Functions of Stomach and intestines Structure of the Pharynx and Oesophagus Pharynx: A tube through which a bolus passes when moved from the mouth to the oesophagus by the process of deglutition The pharynx is divided into three parts namely o Nasopharynx o Oropharynx o Laryngopharynx The Oropharynx is important for digestive system The wall of the pharynx consists of three layers These are the Mucosa, Middle layer (Fibrous tissue) and Outer layer consisting of Smooth muscles involved in swallowing When food enters the pharynx swallowing is no longer under voluntary control Stomach and Intestines The oesophagus is a narrow muscular tube about 25 centimetres long diameter of 2cm, which starts at pharynx at the back of the mouth It passes through the thoracic diaphragm, and ends at the cardiac orifice of the stomach It lies in the median plane in the thorax in front of the vertebral column behind the trachea and the heart. The oesophagus has 4 constrictions where adjacent structure produce impression 1st at the beginning approximately 15cm from the incisor teeth and caused by the cricopharyngeus muscles – upper oesophageal sphincter 2nd where it crossed by the arch of aorta 22.5cm from the incisor teeth 3rd where it crossed by the left main bronchus 27.5cm from the incisor 4th Where it passes through the diaphragm – lower oesophageal sphincter At the top of the oesophagus, is a flap of tissue called the epiglottis that closes during swallowing to prevent food from entering the trachea (windpipe) It has four layers; from outside: o The adventitia o Muscular layer; the muscles are striated (voluntary) in the upper third and mixed (striated & smooth) in the middle and smooth (involuntary) in the lower third There are two layers: The inner is circular The outer is longitudinal o Sub-mucosa layer o Mucosa layer which is made up of stratified squamous epithelium Arterial blood supply of the oesophagus is through oesophageal arteries, branches of thoracic aorta, inferior phrenic arteries and the left gastric branch of the celiac artery Venous drainage is through the azygos and hemiazygos veins Structure and Functions of the Stomach What is a stomach? The stomach: The most dilated part of the gastrointestinal tract Has a J-like shape Positioned between the abdominal oesophagus and the small intestine, the stomach is in the epigastric, umbilical and left hypochondrium regions of the abdomen Its shape and size varies from person to person; even within the same individual its size and shape change from time to time depending on its food contents and the moisture of the body and in adult capacity range from 1.0 to 1.5 litre Structure of the Stomach The stomach is divided for descriptive purposes into four regions by arbitrary lines drawn on its external surface which are o The outlet of the stomach (pyloric orifice) is marked on the surface of the organ by the pyloric constriction and surrounded by a thickened ring of gastric circular muscle (the pyloric sphincter) The pyloric orifice is just to the right of midline in a plane that passes through the lower border of vertebra LI (the trans pyloric plane) Other features of the stomach include: o The greater curvature, which is a point of attachment for the gastro splenic ligament and the greater omentum o The lesser curvature, which is a point of attachment for the lesser omentum o The cardial notch, which is the superior angle created when the oesophagus enters the stomach o The angular incisure, which is a bend on the lesser curvature The stomach is lined with simple columnar epithelium The epithelium forms numerous tube like gastric pits, which are the opening of the gastric glands The epithelial cells of the stomach are of five types The first type is surface mucous cells which produce mucus, is on the surface and lines the gastric pits The remaining four cell types are in the gastric glands They are mucous neck cells which produce mucus; parietal (oxyntic) cells which secrete hydrochloric acid and intrinsic factor needed for vitamin B12 absorption; Chief (zymogenic) cells which produce pepsinogen and endocrine cells, which produce regulatory hormones STOMACH Blood supply of the stomach; a rich arterial supply, arise from the celiac trunk and its branches. Most of the blood is supplied by anastomoses formed along the lesser curvature by the right and left gastric arteries and, along the greater curvature, by the right and left gastro omental artery (gastroepiploic artery) The fundus and upper body of stomach receive blood from the short and posterior gastric arteries branches of the splenic artery Venous drainage is through gastric veins parallel the arteries in position and