CH 25: The Digestive System Flashcards
Digestive tract structures
- mouth
- pharynx
- esophagus
- stomach
- small intestine
- large intestine
Accessory organs of the digestive tract
- teeth
- tongue
- salivary glands
- pancreas
- liver
- galbladder
2 movements of digestive materials
Peristalsis: the muscularis externa propels material through the digestive tract
Segmentation: material is churned and fragmented and at the same time is propelled through the digestive tract by peristaltic contractions
Mesenteries
fused double sheets of peritoneal membrane
Mesenteries functions
- stabilize the organs
- stabilize the position of blood vessels
- provide the attachment of blood vessels going to and from the small intestine
Structures within the oral cavity
- tongue
- uvula
- pharyngeal arches
- salivary glands
- teeth
The roof of the oral cavity consists of
Hard palate: palatine process of the maxilla and palatine bone; separates the oral cavity from the nasal cavity
Soft palate: seperates the oral cavity from the naso pharynx; makes up the palatoglossal arch / palatopharyngeal arch / uvula
The floor of the oral cavity consists of
the tongue
Where are the palatine tonsils found?
between the palatoglossal and palatopharyngeal arches; lateral to the uvual
Functions of the tongue
- manipulation of food
- sensory analysis
- secretion of enzymes to aid in fat digestion
- movement for the formulation of words
- controlled by CNXII
Areas of the tongue
Body: anterior portion of the tongue
Root: posterior portion of the tongue
Dorsum: superior portion of the tongue containing the filiform papillae
Filiform papillae
- provide friction
- conical, pointed, and keratinized
- roughen the tongue
- enable grasping and manipulation of food
- whitish appearance of tongue
Lingual frenulum
thin fold of mucous membrane that attaches the tongue to the floor of the mouth
Ankyloglossia
short lingual frenulum
3 pairs of salivary glands
parotid: primary serous secretions (watery)
sublingual: watery+mucusy
submandibular: primary mucus secretions (thick)
List anatomical structures of the teeth
- crown
- neck
- root
- dentine
- pulp cavity
- root canal
- periodontal ligament
Crown
- covered by enamel
- consists of dentine
- consists of pulp (highly vascularized)
Enamel
made of 97% hydroxyapatite crystals (hard, compression)
Neck
area of gingivia
Root
consists of root canal
consists of artery, vein, and nerve
Dentine
- 70% hydroxyapatite crystals
- mineralized matrix of hydroxyapatite
- different than bone; NO cells
Pulp cavity
spongey area and highly vascularized
Root canal
arteries, veins, and nerves pass through the root canal to te pulp cavity area
Periodontal ligament
- function
- type of articulation
- anchors the root of the tooth to the alveolar sockets
- gomphosis articulation
Types of teeth + functions
4 incisors per jaw: cutting
2 canines per jaw: piercing
4 premolars per jaw: small gnashers
6 molars per jaw including wisdom teeth: large gnashers
Deciduous teeth
20 (baby teeth)
Permanent teeth
32
Pharynx
serves as a common passageway for food, liquid, and air
Esophagus
a hollow muscular tube that extends from the pharynx region to the stomach
Located posterior to the trachea
Innervated by the vagus nerve from the esophageal plexys
Contains upper and lower esophageal sphincters
What happens when the lower esophageal sphincters are not closed all the way?
heart burn / acid reflux
Functions of the stomach
- bulk storage of ingested food
- mechanical breakdown of ingested food
- chemical digestion of ingested food; results in CHYME
Anatomical structures of the stomach
lesser curvature
greater curvature
cardia
fundus
body
pylorus
gastric rugae
relaxed stomach: mucosa forms numerous muscular ridges
permits the expansion of the stomach
stretched stomach exhibits less prominent rugae
Normal stomach distention
stomach is highly distensible
lined with internal fold (gastric rugae)
3x larger during big meals
Extreme distention in competitive eaters
collagen fibers of the stomach lengthen
irreversible stretching causes malnutrition, vomitting, etc
Stomach lining tissue and structures
simple columnar epithelium for absorption and secretion
contains gastric pits and gastric secretory cells
Types of gastric secretory cells
mucous neck cells
parietal cells
chief cells
enteroendocrine cells
Mucus neck cells
modified goblet cells
produce mucus to lubricate the food entering the stomach
protects stomach walls from acid
Parietal cells
secrete hydrochloric acid
kills microorganisms and activates pepsinogen
Chief cells
secrete pepsinogen, which gets converted into PEPSIN by hydrochloric acid
(pepsin digests peptide bonds)
Enteroendocrine cells
produces hormones
G CELLS: produce hormone gastrin
Gastrin
causes parietal and chief cells to release their products
Small intestine +length
structures +length
20 ft long; longest structure in the digestive system
DUODENUM: 10 in long
JEJUNUM: 8 ft long
ILEUM: 12 ft long
Duodenum
entrance to to the small intestine containing the HEPATOPANCREATIC SPHINCTER
Hepatopancreatic sphincter
opens for bile from the liver and galbladder
and for buffers and digestive enzymes from the pancreas
Jejunum
prominent plicae + villi
most nutrient absorption occurs here
Ileum
absorbs anything the jejunum missed
contains prominent lympoid centers (aggregated lymphoid nodules/Peyer’s patches) that regulate gut flora
Large intestine length + diameter
+regions
5 ft long, 3 in diameter
cecum
ascending colon
transverse colon
descending colon
sigmoid colon
rectum
Function of the large intestine
resorption of water and salts to compact waste into feces
absorption of vitamins produced by housed bacteria (vitamin K)
stores fecal material before defacation
Cecum
ileum connects to the medial surface of the cecum
contains the ileocecal valve
veriform appendix attaches to the cecum ~9cm long
Ileocecal valve
regulates the movement of material from the ileum to the cecum
Colon regions
ascending colon
transverse colon
descending colon
sigmoid colon
Haustra
pouches of the colon wall that allow expansion
Taeniae coli
longitudinal muscles that aid in the process of peristalsis
Omental appendices
numerous “flaps” of sacs of fat extending from the intestines and attached to the serosa of the large intestines
Rectum
temporarily stores waste matter
last portion is the anal canal
Know the structures: anal canal, anal columns, anus, internal anal sphincter, external anal sphincter
Accessory organs of digestion
liver
gallbladder
pancreas
Liver
largest visceral organ of the body
in charge of metabolic regulation and bile production
Metabolic production of the liver
filters/detoxifies blood
all blood leaving the digestive tract enters the liver through the hepatic portal system
hepatocytes adjust the circulating metabolites before blood enters the systemic circuit
Bile production of the liver
bile is made by hepatocytes
stored in the gallbladder between meals
secreted into the duodenum during a fatty meal
emulsifies fat in small intestine
emulsification process
makes it easier for lipase to do the actual digestion of fat
Gallbladder
stores bile
cystic duct leads from the neck of the gallbladder to the common bile duct
What’s inside the lobules of the pancreas?
consists of lobules containing acinar cells and islets
Acinar cells
exocrine function
produce digestive enzymes
enzymes travel through pancreatic duct to the small intestine
Pancreatic cells
endocrine function
produce hormones
hormones enter the bloodstream to travel to target organs
