Lect. 17/18 - Digestive system Flashcards
Basic functions of the digestive system (6)
Ingestion Secretion Mixing and propulsion Digestion Absorption Defecation
Layers of the GI tract
Mucosa, submucosa, muscularis, serosa
3 layers of the mucosa
- Lining of epithelium
- Lamina propria
- Muscularis mucosa
Eptihelium in mouth, pharynx, esophagus and anal canal serves a ____ function
protective
Epithelium in the stomach and intestines functions in ___ and ____
secretion and absorption
Every __ to __; epithelial cells are replaced by new ones
5 to 7 days
2 types of cells within the absorptive epithelial cells
Exocrine cells = secrete mucous and fluid into the lumen
Endocrine cells = secrete hormones into the bloodstream
Roles of the lamina propria layer (2)
supports the epithelium and binds it to the muscularis mucosa
- also contains MALT
what is MALT
mucosa-associated lymph tissue
Roles of the muscularis mucosa (2)
increases the surface area for digestion and absorption
- movement of muscle ensures that all absorptive cells are fully exposed to contents of the GI tract
Content of submucosa (1)
Meissner’s plexus
What is meissner’s plexus
portion of the Enteric nerve plexus - ENS (“brain of the gut”)
why is meissner’s plexus important
important in controlling secretions in the GI tract
Muscularis layer - involuntary contractions help in 3 ways
- help break down food physically
- mix it with digestive secretions
- propel it along the GI tract
muscularis layer contains what
second plexus of the ENS - myenteric (auerbach) nerve plexus
role of myenteric nerve plexus
controls primarily the frequency and strength of contraction of the muscularis
serosa layer + other name
superficial layer
also called visceral peritoneum on structures inferior to the diaphragm
Layers of the peritoneum
Parietal peritoneum
Visceral peritoneum
Peritoneal cavity
peritoneum - lines the wall of the abdominopelvic cavity
parietal peritoneum
peritoneum - covers some organs in the cavity and forms their serosa
visceral peritoneum
peritoneum - thin space between the parietal and visceral peritoneum (contains serous fluid)
peritoneal cavity
what is the largest peritoneal fold?
greater omentum
hangs loosely over the transverse colon and coils of SI
double sheet that folds back on itself
greater omentum
name the other peritoneal folds (4)
falciform ligament
lesser omentum
mesentery
mesocolon
attaches the liver to the anterior abdominal wall and diaphragm
falciform ligament
arises as 2 folds in the serosa of the stomach and duodenum + suspends stomach and duodenum from liver
lesser omentum
binds the SI to the posterior abdominal wall (pied de choufleur)
mesentery
fold of peritoneum which binds the LI to the posterior abdominal wall
mesocolon
cheeks, hard and soft palate, tongue
the mouth
what is the labial frenulum
fold of mucous membrane that attaches the lips to their corresponding gums
what forms the hard palate (2)
maxilla and palatine bones
what is the uvula
muscular process hanging from the free border of the soft palate
what is the soft palate
muscular separation between oropharynx and nasopharynx
the mouth - palatine tonsils location
situated between the arches
the mouth - lingual tonsils location
situated at the base of the tongue
the mouth - fauces
opening between the oral cavity and the pharynx (throat)
when food enters the mouth, secretion from the salivary glands ___ and chemical breakdown of food begins
increase
roles of salivary glands when secreting saliva (2)
keep mucous membrane of mouth and pharynx moist
cleanse the mouth and teeth
3 major salivary glands
parotid glands
submandibular glands
sublingual glands
salivary glands - located inferior and anterior to the ears, btw the skin and masseter muscle
parotid glands
how does the parotid gland secrete saliva into the oral cavity?
via the parotid (Stensen’s) duct
salivary glands - found beneath the base of the tongue in the posterior part of the floor of the mouth
submandibular glands
where do the submandibular (Wharton’s) ducts enter the oral cavity?
lateral to the lingual frenulum
salivary glands - superior to submandibular glands
sublingual glands
which ducts open into the floor of the mouth?
lesser sublingual (Rivinus) ducts
salivary glands - sympathetic innervation
initiates vasoconstriction = decrease production of saliva
salivary glands - parasympathetic innervation
initiates vasodilation = increase production of saliva
what are the two important components of the saliva (made of mostly water)
salivary amylase
lingual lipase
what can also stimulate secretion in saliva
smell, sight, sound or thought of food
the tongue attaches to which 3 bones
hyoid bone, styloid process, and mandible
extrinsic muscles of the tongue(3)
hyoglossus, genioglossus, styloglossus
role of extrinsic muscles of the tongue
move the tongue from side to side and in & out to maneuver food
role of intrinsic muscles of the tongue
alter shape and size of tongue for speech and swallowing
dorsal and lateral surfaces of the tongue are covered with papillae (4)
fungiform papillae
filliform
circumvallate
foliate papillae
which papillae of the tongue don’t have taste buds?
Filliform
what is deglutition
mechanism that moves food from the mouth to the stomach
condition where a person’s lingual frenulum is abnormally short or rigid impairing eating and speech
ankyloglossia
condition where sometimes a portion of the stomach pierces through the esophageal hiatus
hiatal hernia
layers of the esophagus
adventitia
muscularis
submucosa
mucosa
3 parts of muscularis layer of esophagus
superior 1/3 = skeletal muscle
middle 1/3 = skeletal and smooth muscle
inferior 1/3 = smooth muscle
content of submucosa layer of esophagus (3)
areolar connective tissue, blood vessels and mucous glands
role of mucosa layer of esophagus
offers protection against abrasion and wear & tear from food particles that are chewed, mixed with secretions and swallowed
Functions of the esophagus (2)
secretes mucous and transports food in the stomach
what controls the passage of food from laryngopharyngeal
upper esophageal sphincter
food is pushed through esophagus by ____ (mechanism)
peristalsis
what is peristalsis
progression of involuntary contraction and relaxation of the circular and longitudinal layers of the muscularis
structure that relaxes during swallowing allowing the bolus to pass into the stomach
located at the narrowing of the esophagus just superior to the diaphragm
lower esophageal sphincter
the stomach connects which 2 structures
connects esophagus to the duodenum
serves as a mixing and holding reservoir since meals are eaten more quickly than intestines can digest and absorb them
stomach
what happens to the macros in the stomach
digestion of starch continues
digestion of protein and triglycerides begins
regions of the stomach (6)
cardia fundus body pylorus lesser curvature greater curvature
stomach - surrounds the superior opening of the stomach
cardia
stomach - rounded portion superior and to the L. of the cardia
fundus
stomach - large central portion, inferior to the fundus
body
stomach - regions that connects to the duodenum
pylorus
3 parts of the pylorus
pyloric antrum
pyloric canal
pyloric sphincter
pyloric antrum
connects to body of stomach
pyloric canal
leads to the duodenum
pyloric sphincter
passageway from pylorus to duodenum
stomach - concave medial border
lesser curvature
stomach - convex lateral border
greater curvature
when the stomach is empty, the mucosa lies in large folds called ?
Rugae
arterial supply of the stomach (4)
R/L gastric arteries
R/L gastroepiploic
Short gastric
stomach - parasympathetic innervation =
vagus nerve (CN X)
stomach - sympathetic innervation =
celiac ganglia
layers of the stomach
mucosa
submucosa
muscularis
serosa
3 parts of the mucosa of stomach
lamina propria
muscularis mucosa
gastric glands
What are gastric glands (part of mucosa)
exocrine glands cells, that secrete their products into the stomach lumen
3 parts of gastric glands
mucous neck cells
chief cells
parietal cells
role of mucous neck cells (stomach)
secrete mucous
role of chief cells (stomach)/
secrete pepsinogen and gastric lipase
role of parietal cells (stomach)
produce HCl and intrinsic factor
mucosa of stomach - includes a type of enteroendocrine cell
G cell
location of G cell + role
pyloric antrum secretes gastrin (hormone) into the blood stream
submucosa layer of the stomach
areolar connective tissue
3 parts of muscularis layer of stomach
outer longitudinal layer
middle circular layer
inner oblique layer
functions of the stomach (2)
mixing waves mix the food with the gastric juice reducing it to ta liquid called chyme
t/f as digestion proceeds, more vigorous waves begins at the body and intensify as they reach the pylorus
true
digestion of proteins being in ___
the stomach
digestion of proteins in mainly achieved by the enzyme ____
pepsin
protein chains of many amino-acids are broken down into smaller fragments called ____
peptides
pepsin also aids in digestion of what
milk proteins
role of gastric lipase (2)
splits the short chain of triglycerides found in milk
limited role in the adult stomach (more pancreatic lipase)
within _ to _ after eating a meal, the stomach usually has emptied its contents into the duodenum
2-4 hours
chemical digestion in the small intestines depends on the activity of which 3 organs?
pancreas, liver and gallbladder
pancreatic duct other name
duct of Wirsung
pancreatic duct joins what and empties where
joins with common bile duct
empties in greater duodenal papillae
accessory pancreatic duct other name
duct of Santorini
accessory pancreatic duct empties where
in lesser duodenal papilla
4 parts of the pancreas
retroperitoneal gland
head
body
tail
arterial supply of the pancreas
sup and inf. pancreaticoduodenal aa.
splenic a.
superior mesenteric aa.
innervation of the pancreas
celiac and superior mesenteric plexuses
pancreas is made up of small clusters of glandular epithelial cells:
- 99% are arranged in clusters called ___
- 1% are organized into clusters called ____
Acini Pancreatic islets (islets of langerhans)
pancreas - exocrine portion of the organ + cells secrete a mixture of fluid and digestive enzymes called pancreatic juice
Acini
pancreas - endocrine portion of the organ + secrete the following hormones : glucagon, insulin, somatostatin & pancreatic polypeptide
Pancreatic islets
stops the action of pepsin in the stomach and creates the proper pH level for action of digestive enzymes in the S.I
pancreatic juice
name the accessory organs of digestive system (8)
Mouth = teethe + tongue sublingual gland submandibular gland parotid gland liver pancreas gall bladder