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