Chapter 23: Digestive System Flashcards
Alimentary canal (gastrointestinal or GI TRACT):
◼️mouth to anus
◼️digests food and absorbs fragments
◼️mouth, pharynx, esophagus , stomach, small intestine, large intestine
Two groups of organs:
◼️alimentary canal
◼️accessory digestive organs
Accessory digestive organs:
◼️teeth, tongue, gallbladder ◼️digestive glands: ▪️salivary glands ▪️liver ▪️pancreas
6 essential activities:
1⃣ingestion 2⃣propulsion 3⃣mechanical breakdown 4⃣digestion 5⃣absorption 6⃣defecation
GI tract regulatory mechanisms:
◼️mechanoreceptors and chemoreceptors
◼️intrinsic and extrinsic controls
Mechanoreceptors and chemoreceptors :
◼️respond to stretch, change in osmolarity and pH , and presence of substrate and end products of digestion
◼️initiate reflexes that :
▪️activate or inhibit digestive glands
▪️stimulate smooth muscle to mix and move lumen contents
Intrinsic and extrinsic controls:
◼️short reflexes: enteric nerve plexuses (gut brain) respond to stimuli in GI tract
◼️long reflexes : respond to stimuli inside or outside GI tract ; involves CNS centers and autonomic nerves
◼️hormones from cells in stomach and small intestine stimulate target cells in same or different organs to secrete or contract
Peritoneum:
◼️serous membrane of abdominal cavity
◼️visceral peritoneum on extern surface of most digestive organs
◼️parietal peritoneum lines body wall
Peritoneal cavity :
◼️between two peritoneums
◼️fluid lubricates mobile organs
Mesentary:
◼Double layer of peritoneum
◼️routes for blood vessels, lymphatics , and nerves
◼️holds organs in place ; stores fat
Retroperitoneal organs:
Posterior to peritoneum
Intra peritoneal :
Surrounded by peritoneum
Peritonitis:
◼️inflammation of peritoneum
◼️causes by ex piercing abdominal wound, perforating ulcer , ruptured appendix
◼️peritoneal covering stick together, localizing infection
◼️dangerous and lethal if widespread
◼️treated with debris removal and antibiotics
Splanchic circulation:
◼️branches of aorta serving digestive organs :
▪️hepatic, splenic, left gastric
▪️inferior and superior mesenteric
Hepatic portal circulation:
◼️drains nutrient -rich blood from digestive organs
◼️delivers it to the liver for processing
Four basic layers of the alimentary canal:
◼️mucosa
◼️sub mucosa
◼️muscularis externa
◼️serosa
Mucosa lines what?
Lines lumen
Mucosa 3 functions:
◼️secretes mucus, digestive enzymes, and hormones
◼️absorbs end products of digestion
◼️protects against infectious disease
Mucosa has what three layers?
◼️epithelium
◼️lamina propria
◼️muscularis mucosae
Epithelium :
◼️simple columnar epithelium and mucus secreting cells (most of tract)
▪️mucus : protects digestive organs from enzymes
And
Eases food passage
◼️May secrete enzymes and hormones (ex: in stomach / small intestine)
Lamina propria:
◼️loose areole connective tissue
◼️capillaries for nourishment and absorption
◼️lymphoid follicles (part of MALT)
▪️defend against microorganisms
Muscularis mucosae:
Smooth muscle ➡️ local movements of mucosa
Sub mucosa :
◼️areolar connective tissue
◼️blood and lymphatic vessels lymphoid follicles, and submucosal nerve plexus
Muscularis externa:
◼️responsible for segmentation and peristalsis
◼️inner circular and outer longitudinal layers
▪️circular layer thickens in some areas ➡️sphincters
▪️myenteric nerve plexus between two muscle layers
What tissue type is Visceral peritoneum?
◼️️areolar connective tissue covered with mesothelium in most organs
Visceral peritoneum is replaced by what __ in the esophagus?
Adventitia
Retro peritoneal organs have both _ and _ ?
Adventitia and serosa
Where does is the intrinsic nerve supply of alimentary canal come from?
Enteric neurons (more than spinal cord)
Major nerve supply to GI tract wall; control motility :
◼️Submucosal nerve plexus
◼️myenteric nerve plexus
Submucosal nerve plexus :
Regulates glands and smooth muscle in the mucosa
Myenteric nerve plexus:
Controls GI tract motility
Enteric nervous system:
◼️linked to CNS via afferents visceral fibers
◼️long ANS fibers synapse with enteric plexuses
▪️sympathetic impulses inhibit digestive activities
▪️parasympathetic impulses stimulate digestive activities
Oral (buccal) cavity:
◼️bounded by lips, cheeks, palate, and tongue
◼️oral office is anterior opening
◼️lined with stratified squamous epithelium
What is the oral cavity lined with?
Stratified Squamous epithelium
Which muscles so the lips and cheeks contain?
◼️Oris
◼️buccinator
Oral vestibule:
Recess internal to lips (Labia) and cheeks, external to teeth and gums
Oral cavity:
Proper lies within teeth and gums
Labial frenulum:
Median attachment of each lip to gum
Hard palate:
◼️Palatine bones and palatines processes of maxillae
▪️slightly corrugated to help create friction against tongue
Soft palate :
Folded form mostly skeletal muscle
What does the soft palate do?
Closes off nasoparynx during swallowing
Uvula projects __ from its free edge ?
Downward
Tongue is what kind of muscle ?
Skeletal
3 functions of the tongue:
◼️repositioning and mixing food during chewing
◼️formation of bolus
◼️initiation of swallowing , speech, and taste
What do intrinsic muscles do with tongue?
Change shape
What do extrinsic muscles do with tongue?
Alter tongues position
Lingual frenulum:
Attachment to floor of mouth
The tongues surface bears 4 papillae:
◼️filiform
◼️fungiform
◼️vallate (circumvallate)
◼️foliate
Filiform:
◼️whitish, give the tongue roughness and provide friction; do not contain taste buds
Fungiform:
Reddish, scattered over tongue; contain taste buds
️Vallate :
V- shaped row in back of tongue; contain taste buds
Foliate:
On lateral aspects of posterior tongue; contain taste buds that function primarily in infants and children
Lingual lipase:
◼️secreted by serous cells beneath foliate and ️vallate papillae secrete
◼️fat-digesting enzyme functional in stomach
Terminal sulcus marks division between:
◼️body- anterior 2/3 residing in oral cavity
◼️root- posterior third residing in oropharynx
◼️just posterior to vallate papillae
