Final exam part one Flashcards
Functions of the digestive system
Ingestion, digestion, propulsion, secretion, absorption, & elimination of wastes
Ingestion
Introduction of solid & liquid materials into the oral cavity. The first step in the process of digesting & absorbing nutrients
Digestion
Breakdown of large foods into smaller structures & molecules. Two aspects: mechanical digestion & chemical digestion
Mechanical digestion
Physically breaks down ingested materials into smaller pieces. First part is mastication, the chewing of ingested material by the teeth in the oral cavity
Chemical digestion
Breaks down ingested material into smaller molecules by using enzymes
Propulsion
Process of moving swallowed materials through the GI tract. Two ways of movement involved: Peristalsis & segmentation
Peristalsis is
The process of muscular contraction that forms ripples along part of the GI tract & forces material to move further along the tract
Segmentation is
Churning & mixing movements in the small intestine. Help disperse the material being ingested & combine it with digestive organ secretions
Secretion is
The process of producing & releasing mucin or fluids such as acid, bile, & digestive enzymes. When these products are secreted into the lumen of the GI tract, they facilitate chemical digestion & the passage of material through the GI tract.
Mucin secretions serve a protective function. How?
Mucin mixes with water to form mucus, which coats the GI wall to protect & lubricate it against acidic secretions & abrasions by passing materials
Absorption involves
Either passive movement or active transport of electrolytes, digestion products, vitamins, & water across the GI tract epithelium & into GI tract blood & lymph vessels
Elimination of wastes
All undigestable materials as well as the waste products secreted by the accessory organs into the GI tract are compacted into feces, or fecal material, & the eliminated from the GI tract by the process of defecation
Hard Palate is
Anterior two thirds of the palate. Formed by the palatine processes of the maxillae & the horizontal plates of the palatine bones. Covered w/dense connective tissue & nonkeratinized stratified squamous epithelium & exhibits transverse palatine folds that assist the tongue in manipulating ingested materials prior to swallowing
Soft palate is
Composed of skeletal muscle & covered w/keratinized stratified squamous epithelium. Posterior part is a projection called uvula. When swallowing, the soft palate & uvula elevate to close off the posterior entrance into the nasopharynx & prevent ingested materials from entering the nasal region
Palatine tonsils are
Housed between the palatoglossal arch & the palatopharyngeal arch. Serve as an “early line of defense” as they monitor ingested food & drink for antigens, & initiate an immune response when necessary
Papillae are
Numerous small projections that cover the superior (dorsal) surface of the tongue.
Lingual tonsils are
Located posteriorinferior surface of the tongue. A collection of lymphoid follicles on the posterior portion of the dorsum of the tongue
Bolus is
The chewed food mixed with saliva. The stomach processes the bolus and turns it into a paste-like substance called chyme.
What is the function of the stomach?
It continues the mechanical & chemical digestion of the bolus. After the bolus has been completely processed in the stomach, the product is called chyme. Facilitates the mechanical digestion by the contractions of its thick muscularis layer, which churns & mixes the bolus & the gastric secretions. Facilitates chemical digestion through its gastric secretions of acid & enzymes
Deciduous teeth are
Also called milk teeth, 20 erupt between 6 months & 30 months after birth in an infant. Eventually lost and replaced by 32 permanent teeth
Lamina propria is
One of three components of mucosa. An underlying areolar connective tissue
What supplies the abdominal GI tract?
Branches of the celiac trunk, superior mesenteric artery, & inferior mesenteric artery
How do the different branches of blood vessels supply the abdominal GI tract?
Branches travel w/in the tunics, & the mucosa contains capillaries that have fenestrated endothelial cells to promote absorption. The veins arising in the mucosa form anastomoses in the submucosa before exiting the wall of the GI tract adjacent to their companion arteries . The veins merge to form the hepatic portal system of veins
Peyer patches are?
Lymphatic structures, aggregate nodules. They appear as oval bodies the size of a pea.
MALT is
(Mucosa-associated lymphatic tissue) Lymphatic structures found in the small intestine & appendix. In the small intestine they are called peyers patches.
Gastric pits
Distinguishes the stomach mucosa from the default pattern. Numerous depressions that indent the stomach.
Gastric glands are?
Several branched tubular glands at the base of each gastric pit. Extend through the length of the mucosa to its base
Gastric juices are produced by?
Cells in the gastric glands, & their secretions are released into gastric pits, which funnel them to the lumen of the stomach
Parietal cells are
located primarily in the proximal & middle parts of the gastric gland. Their features are small intracellular channels called canaliculi, which are lined by microvilli. Hydrochloric acid secreted across the cells surface helps denature proteins to facilitate chemical digestion. They produce intrinsic factor.
Intrinsic factor is
A molecule that binds vitamin B12 in the stomach to lumen & assists in B12 absorption in the ileum of the small intestine
Chief cells are
Housed primarily in the distal part of the gastric gland. Synthesize & secrete enzymes, primarily inactive pepsinogen, into the lumen of the stomach. The acid content of the stomach then converts inactive pepsinogen into the active enzyme pepsin
Pepsinogen is
An enzyme synthesized & secreted by chief cells. It is inactive until the acid of the stomach converts it to the active enzyme pepsin, which chemically digests denature proteins in the stomach into smaller fragments
Gastrin is
A hormone that enters the blood and stimulates the secretory activities of the chief & parietal cells & the contractile activity of gastric muscle
Enteroendocrine cells are
Endocrine cells widely distributed in the gastric glands of the stomach. Secrete gastrin & produce other hormones, like somatostatin, that modulate the function of nearby enteroendocrine & exocrine cells
Function of the small intestine is
Finishes the chemical digestion process & is responsible for absorbing up to 90% of the nutrients & water. Ingested nutrients spend at least 12 hours in the small intestine as chemical digestion & absorption are completed
Villi is
Small fingerlike projections of mucosa in the circular fold in the small intestine. They further increase the surface area for absorption & secretion
Microvilli in the small intestine are
Increasing the absorptive surface area even further. Along the free surface of the simple columnar cells. Individual microvilli are not clearly visible in light micrographs of the small intestine; they collectively appear as a brush border.
Brush border are
Microvilli that resembles a brightly staining surface on the apical end of the simple columnar cells
Lacteals in the small intestine are
Responsible for absorbing lipids & lipid soluble vitamines, which are too large to be absorbed by the capillaries
Intestinal glands are
Invaginations of mucosa. Also known as intestinal crypts or crypts of lieberkuhn. Extend to the base of the mucosa & slightly resemble the gastric glands of the stomach. They are lined w/simple columnar epithelial cells (w/goblet cells) & enteroendocrine cells
Function of intestinal glands in the small intestines
Increase surface area for both absorption & chemical digestion; enteroendocrine cells lining intestinal glands secrete digestive hormones
Brunner glands are
Also called submucosal glands. Produce a viscous alkaline mucus that protects the duodenum from the acidic chyme
Function of goblet cells in the small intestine
Produce mucin to lubricate & protect the intestinal lining as materials being digested pass through
What role do the plicae circulares play in the small intestine?
Also called circular folds, they slow down PG 799
Digestive enzymes of the small intestine
Enteroendocrine cells release hormones such as secretin, cholecystokinin, & gastric inhibitory peptide. Some of these hormones temp. slow down digested activities as material from the stomach begins to enter the small intestine, prolonging the time for the stomach emptying into the small intestine
Surface area in the small intestine
The circular folds; on the folds the villi & microvilli increase surface area
Peritoneum of the large intestine
Anterior surface of the ascending colon is covered w/peritoneum
Mesenteries are
Folds of peritoneum that support & stabilize the intraperitoneal GI tract organs. Blood vessels, lymph vessels, & nerves are sandwiched between the two folds & supply the digestive organs
Greater omentum
Extends inferiorly like an apron from the greater curvature of the stomach & covers most of the abdominal organs. Often accumulates large amounts of adipose connective tissue
Lesser omentum
Connects the lesser curvature of the stomach & the proximal end of the duodenum to the liver. May be subdivided into a hepatogastric ligament, which runs from the liver to the stomach, & the hepatoduodenal ligament, which runs from the liver to the duodenum
Peritoneum is
The portion of the serous membrane that lines the inside surface of the body wall, is called the parietal peritoneum. The portion that folds back (reflects) to cover the surface of internal organs is called the visceral peritoneum. Between these two layers is the peritoneal cavity
Peritoneal cavity is
Potential space where the peritoneal layers that face each other secrete a lubricating serous fluid. This thin layer of fluid lubricates both the wall & the internal organ surfaces, allowing the abdominal organs to move freely, & reducing any friction resulting from this movement
Intraperitoneal organs
W/in the abdomen, organs that are completely surrounded by visceral peritoneum. Stomach, part of duodenum, jejunum, ileum, cecum, appendix, & transverse & sigmoid colon
Retroperitonial organs
Lie directly against the posterior abdominal wall, only their anterolateral portions are covered w/peritoneum. Include most of the duodenum, pancreas, ascending/descending colon & the rectum
Functions of the liver
Producing bile, hepatocytes detoxify drugs, metabolizes, & poisons
Falciform ligament is
A peritoneal fold that secures the liver to the anterior abdominal wall
Round ligament of the liver is
Ligamentum teres, represents the remnant of the fetal umbilical vein
The hepatic triad of the liver is
Composed of branches of the hepatic portal vein, the hepatic artery, & the bile duct. At the periphery of each lobule, also called portal triads
Hepatic sinusoids are
Bordered by cords of hepatocytes. Thin walled, porous or “leaky” capillaries where venous & arterial blood are mixed & then flow slowly through the hepatic lobule toward the central vein. Lined w/ stellate cells called reticuloendothelial cells (Kupffer cells)
Kupffer (reticuloendothelial) cells are
Phagocytic cells that have an immune function. They line the sinusoids
Bile production
Hepatocytes absorb nutrients from the sinusoids, & they also produce bile. Between each cord of hepatocytes is a small bile canaliculus which conduct bile from the hepatocytes to the bile duct in the portal triad
Gallbladder is
Attached to the inferior surface of the liver. Concentrates bile produced by the liver & stores this concentrate until it is needed for digestion
What is the pancreas head?
It is adjacent to the curvature of the duodenum
What is the body of the pancreas?
Central elongated body projecting towards the left lateral abdominal wall
Function of the large intestine
Absorbs most of the water & ions from the remaining digested material. In so doing, the watery material the first enters the large intestine soon solidifies & becomes feces. The large intestine stores the feces until the body is ready to defecate (expel the feces). Also absorbs a small percentage of nutrients still remaining in the digested material
Function of circular folds of the small intestine
Slow down the passage of materials undergoing digestion; increase surface area for both absorption & chemical digestion
Function of Villi of the small intestine
Increase surface area for both absorption & chemical digestion
Function of microvilli of small intestine
Increase surface area for both absorption & chemical digestion
Function of intestinal glands of the small intestine
Increase surface area for both absorption & chemical digestion; enteroendocrine cells lining intestinal glands secrete digestive hormones
Chyme is
When the stomach processes the bolus & turns it into a paste-like substance called chyme
HCL of the stomach is
Hydrochloric acid secreted by parietal cells. Helps denature proteins to facilitate chemical digestion.
Permanent teeth
Replace deciduous teeth. There are 32 permanent teeth.
Reverse peristalsis is
Antiperistalsis A wave of contraction of GI tract smooth muscle which moves contents orally.
Masticate is
Chewing, this involves mixing food with saliva, which contains an enzyme called salivary amylase which partially digests the food
Adventitia is
One of the four concentric layers (tunics) of the GI tract. Composed of areolar connective tissue with dispersed collagen & elastic fibers.
What is the difference between adventitia and serosa?
Serosa has the same components as the adventitia, but is covered by a visceral peritoneum.
What are the circular muscles of the gut wall in the muscularis layer?
Fibers of the inner layer of smooth muscle are oriented circumferentially around the GI tract, and are called the inner circular layer
What are the longitudinal muscles in the muscularis layer of the gut wall?
The fibers of the outer layer are oriented lengthwise along the GI tract, and are called outer longitudinal layers
Lymphatics of the gut wall
Lymphatic capillaries arise as blind tubes in the mucosa of the GI tract. In the small intestine, each villus usually contains a single, blind-ended, central lymphatic capillary called a lacteal.
Responsible for absorbing dietary lipids & lipid soluble vitamins
Lacteal
Outside the organ walls, lymphatic capillaries merge to form
Lymphatic vessels. These vessels enter & exit the many lymph nodes scattered near the organs & w/in the mesentery. This lymph will be transported to the cisterna chili, which drains into the thoracic duct
The lymphatic structures within the GI tract lie primarily in the
Lamina propria of the mucosa.
Goblet cells
Produce mucin to lubricate & protect the intestinal lining as materials being digested pass through
Glandular epithelial cells found in the lining of the digestive and respiratory tracts. They are used to secret mucus. Mucus is a sticky, viscous substance composed of mucins, enzymes and electrolytes.
Goblet cells
Plicae circulares are
Numerous permanent crescentic folds of mucous membrane found in the small intestine especially in the lower part of the duodenum and the jejunum
What provides most of ATP?
Mitochondria
Circular folds, which can be seen with the naked eye, help increase the surface area through which nutrients can be absorbed. Act like speed bumps to slow down the movement of chyme & ensure that it remains w/in the small intestine for maximal nutrient absorption. More numerous in the duodenum & jejunum, and least numerous in the ileum
Plicae circulares
Why is the pancreas referred to as a mixed gland?
Because it exhibits both endocrine & exocrine functions.
Endocrine functions of the pancreas
Performed by the cells of the pancreatic islets
Exocrine functions of the pancreas
Results in the secretion of digestive enzymes & bicarbonate, collectively called pancreatic juice, into the duodenum
Acinar cells in the pancreas
The pancreas contains modified simple cuboidal epithelial cells called acinar cells. These cells which are organized into clusters termed acini, or lobules, secrete the mucin & digestive enzymes of the pancreatic juice.
Anatomy of the pancreas
Has a wide head adjacent to the curvature of the duodenum, a central elongated body projecting toward the left lateral abdominal wall, and a tail that tapers as it approaches the spleen
Pancreatic islets are
Also called islets of Langerhans, are tiny clusters of cells scattered throughout the pancreas. Pancreatic islets contain several types of cells, including beta cells, that produce the hormone insulin.
Egestion is
The process of removing undigested food that is stored in the rectum and its eventual passing through the anus as faeces. When we eat, water is absorbed back into the body in the large intestine and the undigested food goes to the lower part of the large intestine
Compaction is
Progressive dehydration of indigestible materials and organic wastes prior to elimination from the body
Histology of Digestive Tract (Deep to Superficial)
Mucosa-submucosa-muscularis-serosa
Lowers PH of gastric juice, kills microorganisms, breaks down food, activates chief cells
HCL
Lobes of liver
Right, left, quadrate, caudate
Between liver and diaphragm
Coronary ligament
Liver lobules are
The basic functional units of liver
