Anatomy of the digestive system Flashcards
What does the digestive tract consist of?
Oral cavity, oesophagus, small and large intestine and the anus
Has associate glands and organs
What is the function of the Digestive tract?
Breakdown food for absorption into the body and to eliminate waste
What are the phases of digestion?
Ingestion Fragmentation Digestion Absorption Elimination
What happens during the ingestion phase of digestion?
Oral cavity receives food and starts mastication
What happens during the fragmentation phase of digestion?
Oral cavity fragments the food by the process of mastication (chewing) and also secretes saliva containing enzymes to begin digestion processes.
What happens during the Digestion phase of digestion?
enzymatic breakdown of food into molecules for absorption. Oral cavity with salivary amylase, continues into the stomach forming chime. The pancreatic enzymes and bile in duodenum, completed as passes through small intestine.
What happens during the absorption phase of digestion?
Most nutrients, amino acids, glucose molecules and water are absorbed in the small intestine. Extra water that is not absorbed is then further absorbed in the large intestine to remove the water from stool.
What happens during the elimination phase of digestion?
Rectum holds faeces prior to defaecation via the anal canal.
Where is the oral cavity?
Extends from the lips to the oropharynx posterior boundary, oropharyngeal isthmus
What is the vestibule?
between the lips and cheek (buccinators muscle) externally and teeth and gums internally
What is the mouth proper?
Anterior and laterally dental arches
floor- anterior 2/3rd of tongue, mylohyoid muscles, geniohyoid muscle
Roof - hard and soft palate
Posteriorly - oropharyngeal isthmus
What are the muscles of the tongue?
Intrinsic muscles - superior and inferior longitudinal, vertical, transverse and septum
Extrinsic muscles - plalatoglossus, styloglossus, hypoglossus, genioglossus.
What are the parotid glands?
Parotid glands produce serous acini - fluid containing amylase and antimicrobial proteins
What are the submandibular and sublingual glands?
Submandibular - mixed serous and mucous gland but predominantly serous acini (amylase, proteins and lysozymes)
Sublignual gland - mixed gland but predominantly mucinous
Where is the soft palate and what is it?
Sits behind the hard palate. swings up when swallowing to prevent food entering the nasal cavity.
What is the pharynx?
Nasopharynx, oropharynx and laryngopharynx.
consists of 3 rings of constrictor muscles (superior, middle and inferior) which contract sequentially when swallowing to squeeze food down the oesophagus.
What is the structure of the gut tube?
Mucosa - epithelial tissue
submucosa -connective tissue, submucosal gland, blood vessels and submucosal nerve plexus
muscularis - inner smooth muscle circular layer, myenteric nerve plexus, outer longitudinal layer
serosa - loose connective tissue, blood vessels and a simple squamous epithelium covering
What are the various regions of the gut?
Foregut - lower part of the oesophagus to mid duodenum supplied by the celiac trunk
mid gut -from duodenum to the transverse colon supplied by the superior mesenteric artery
hindgut - transverse colon to mid anal canal supplied by the inferior myenteric artery
What is the oesophagus?
Muscular tube ranging from the laryngeal pharynx to the stomach.
What is the histology of the oesophagus?
Stratified squamous epithelium (non keratinised)
submucosal mucous secreting oesophageal glands
What is the location of the stomach?
Upper stomach frim the left costal margin into the epigastrium and umbilical regions
fixed at ends but mobile in between
depends on volume of content, body position and phase of respiration.
What is the function of the liver?
secretion of bile
What is the Exocrine function of the pancreas?
Produce enzymes to hydrolyse proteins fats and carbohydrates
what blood supply supplies the foregut and what nerves innervate the foregut?
Blood Supply - Coeliac Trunk
Venous Drainage - Portal and splen vien
Innervation - Symp and Parasymp (vagus)
what blood supply supplies the midgut and what nerves innervate the midgut?
Blood Supply - Superior mesenteric artery
Venous Drainage - Superior mesenteric vein
Innervation - Vagus nerve of ParaNS
What is the Endocrine function of the Pancreas?
Production of insulin and glucagon for carbohydrate metabolism
what blood supply supplies the hindgut and what nerves innervate the hindgut?
Blood Supply - inferior mesenteric artery
Venous Drainage - Inferior mesenteric vein
Innvervation - Pelivic nerves, inferior mesenteric plexus
What is the Duodenum?
D1 - Superior part: from pylorus to the neck of the gallbladder
D2 - Descending part: just to the right of the midline and contains the major and mino dudenal papilla
D3 - inferior part: crosses the IVC and aorta and the vertebral column
D4 - ascending part: passes upwards to the left of the aorta terminating at the duodenojejunal flexure
How does the duodenum get its blood supply?
Coeliac trunk - common hepatic artery
superior mesenteric artery
How does the stomach get its blood supply
Coeliac trunk - Splenic artery
Common hepatic artery
What is the anatomy of the liver surface?
Inferior to the diaphragm
covered by lower ribs and costal cartilages
gallblader - tip of the 9th costal cartilage in the midclavicular line
How does the liver get its blood supply?
Hepatic portal vein (70%)
Hepatic artery proper (30%)
What is the histology of the liver>
Hepatocytes arranged into lobules
blood vessels and bile ducts at the corners of the lobules
bile carrier from hepatocytes in canaliculi to bile ducts which merge and enlarge into the hepatic ducts
What is the anatomy of the gallbladder?
Lies in the gallbladder fossa on the visceral surface of the liver
Pear shaped sac
stores bile produced by the liver, concentrates it and then releases it into the duodenum in response to the presence of fatty foods
What are the pancreatic ducts?
The exocrine pancreas secretes the alkaline fluid in response to the release of secretom.
Main pancreatic duct
Accessory pancreatic duct
What is the histology of the pancreas?
Endocrine - Islets: Alpha cells - glucagon beta cells - insulin delta cells - somatostatin PP cells - pancreatic polypeptide
Exocrine - Acini:
Acinar cells produce and store enzymes in an inactive form in secretory granules
What is the jejunum?
The part of the small intestine between the duodenum and the ileum
What is the Ileum?
The 3rd portion of the small intestine between the jejunum and the caecum
What is the histology of the small intestine?
SUbmucosal folds - plicae cirulares
Mucosal Outgrowths - vili
Goblet cells - mucous producing
What is the function of the large intestine?
Absorption of water and electrolytes
Storage and expulsion of undigested material
What is the anatomy of the large intestine?
Caecum Ascending colon hepatic flexure transverse colon splenic flexure Descending colon Sigmoid colon Rectum Anal Canal
What are some features of the large intestine?
Fat filled peritoneal tages - appendicies epiploe on external surface
Outer longitudinal muscle
Taeniae
What artery supplies the large intestine?
Inferioir mesenteric artery
What is the histology of the large intestine?
Tubular intestinal glands
colonocytes - simple columnar epithelium
Goblet cells
Where is the rectum?
The final section of the large intestine terminating at the anus, composed of three lateral curves and the lower part widens into the rectal ampulla
Where is the Anal Canal?
Rectal ampulla to the anus Contains internal (smooth muscle) and external (skeletal muscle) anal sphincters
What is the histology of the rectum and anal canal?
Simple columanr glandular epithelium of rectum which changes to stratified squamous epithelium in the anal canal
What is the peritoneum?
The serous membrane lining the cavity of the abdomen and overing the abdominal organs.
Parietal peritoneum - lines abdominal cavity
Visceral peritoneum - covers organs
What is the peritoneal cavity?
A potentialspace between the parietal and visceral peritoneums
What is the structure of the peritoneal cavity?
Lesser and greater sac
What are Omenta?
A fold of peritoneum connecting the stomach with the other abdominal organs.
This can seal off and localise infections
What are Mesenteries and what do they do?
A fold of the peritoneum that attaches the stomach, small intestine, pancreas, spleen and other organs to the posterior wall of the abdomen.
It carries blood vessels, nerves and lymphatic vessels
What do the peritoneal ligaments do?
Connect organs to each other and the body wall
