BIO - Ch. 28: Digestive System Flashcards
Digestion Process
Mouth>Pharynx>Esophagus>(Lower Esophageal or cardiac sphincter)Stomach (cardia>undus>body>pylorus)>(Pyloric sphincter)>Small Intestine>(Duodenum Jejunum, Ileum)>Large Intestine (cecum, colon(ascending, transverse, descending, sigmoid))>Rectum>Anus
GI
GI: stomach/intestine
4) Layers: Serosa (outer-thin), Submucosa (glandular-thick), Muscularis (mm), Mucosa (innermost-mucous
Mouth
Hard palate bones: two maxillae/two palatines
Soft palate: between the mouth and nasopharynx Uvula (“punching”)
Papillae (bumps on tongue)
Lingual frenulum anchors tongue to the floor of the mouth
Intrinsic mm (speech/mastication)
extrinsic mm (swallowing/speech)
Mouth Salivary Glands
Parotid glands: largest salivary glands (produce watery saliva containing enzymes) Submandibular glands: contain enzyme (amylase) and mucus producing
Sublingual glands: smallest salivary glands; produce a mucous saliva
- Buccal glands provide hygiene/comfort of oral
tissues
Pharynx
From the mouth to the esophagus
ESOPHAGUS
first segment of the digestive tube lined with voluntary/involuntary m tissue & epithelium (protects from abrasion)
Upper m sphincter: prevents air from entering during respiration/permits belching
Lower m sphincter: holds food in stomach
STOMACH
upper part of the abdominal cavity under the liver/diaphragm - L of midline
Divisions:
- Cardia (junctions with esophagus)
- Cardiac Sphincterstyle
- Fundus (opening of esophagus into
stomach)
- Body
- Pylorus
- Pyloric Sphincter (bwtn stomach to
duodenum)
Greater curvature at lower L regionSTOMACH WALL
Epithelial lining has rugae (gastric pits)
Gastric Glands: secrete gastric juice (found below pits)
Pepsin enzyme released (digest proteins)
Secretory Cells of the gastric gland:
- Cheif (gastric juice enzyme)
- Parietal (hydrochloric acid - absorb B12)
- Endocrine (ghrelin - stimulates
hypthalamus > GH > Breaks down food (limited absorption)
Helps protect the body from pathogenic bacteria (from food)
SMALL INTESTINE
Most nutrient absorption occurs
Divisions:
- Duodenum (uppermost division attach to pyloric section)
- Jejunum
- illeum (connects to lg intestine)
Intestinal lining comprised of plicae (folds) and villi/microvilli (incr surface are - incr absorption/digestion)
Crypts: between villi (continually renewed intestinal mucosa)
LARGE INTESTINE
Cecum: first 2/3 of Lg intestine
Colon: Ascending (contains ileocecal valve: prevents material going back into ileum of small intestine), Transverse, Descending, Sigmoid (btwn descending/rectum)
Rectum > anal canal > internal/external mm of the anus
APPENDIX
Accessory organ
Communicates with cecum (Lg intestine)
Contains non-pathogenic intestinal bacteria to aid in absorption of nutrient
Function non understood
PERITONEUM
Mesentery projection allows free movement of each coil of the intestine, helps prevent strangulation of the long tube
LIVER
Largest gland in the body
L-Lobe (1/6th of liver) R-Lobe (5/6th of liver)
Falciform ligament (seperates lobes)
Vessels:
- Hepatic ducts: carry bile salts (digest fats/breakdown bilirubin from old RBCs) created in
the liver to the gallbladder for storage
- Hepatic artery: carries oxygenated blood to the liver
- Portal vein: carries deoxygenated blood from the stomach and intestines to the liver to be
cleansed and toxins removed
GALLBLADDER
Storage of bile and concentration of bile
Ejection of the concentrated bile into the duodenum
PANCREAS
Exocrine portion (majority of the pancreas): arrangement of tiny ducts unite to form main pancreatic duct (empties into the duodenum secreting digestive enzymes)
Endocrine portion: pancreatic islets (passes secretions into capillaries)
Function:
- Acinar units secrete digestive enzymes
- Beta cells secrete insulin
- Alpha cells secrete glucagon
Mastication & Deglutition
Mastication: act of chewing
Deglutition: process of swallowing
- Oral stage (mouth > oropharynx)
- Pharyngeal stage (oropharynx to
esophagus): propel bolus from pharynx >
esophagus (mouth/nasopharynx/larynx
must be closed)
- Esophageal stage (esophagus to stomach)Peristalsis & Segmentation
Peristalsis: wavelike ripple causing forward movement of matter along the GI tract
- Occurs in the esophagus, stomach, small/large intestine
Segmentation: mixing movements of gastric juices
Gastric Emptying
Hormonal mechanism: enterogastric reflex fats in duodenum stimulate the release of gastric inhibitory peptide (decreases peristalsis of gastric m slows passage of chyme into duodenum) to keep the small intestines from being overburdened
Nervous mechanism: receptors in the duodenum are sensitive to acid and distention =
impulses over sensory/motor fibers in the vagus nerve to cause a reflex inhibition of gastric
peristalsis
(6) Chemical Substances
carbohydrates (mouth/sm intestine - amylase maintained by sodium bicarbonate & HCL) proteins (stomach - protesases) fats (duodenum - lipase) vitamins mineral salts water
Protein Digestion
Broken down by proteases:
- pepsin (from gastric juice in stomach) and trypsin (pancreatic juice)
Fat Digestion
Emulsification is the breaking down of fats into smaller droplets = water soluble
Bile (sent to the duodenum) finishes emulsification > complete digestion by lipase (sent from pancrease)
Digestive Gland Secretion
All of the digestive juices are controlled by hormonal reflex mechanisms and nervous reflex mechanisms
Hormones involved in secretion of digestive juices: gastrin, gastric inhibitory peptide, & secretin
Absorption Pathways
Circulatory System: substances from protein/carbs are absorbed by the blood > liver (portal vein) > heart
Lymphatic System: substances from fats are absorbed by lacteals > heart
