Digestive System COPY Flashcards
Wall of Esophagus
From deep to superficial:
- Mucosa
- Submucosa
- Muscular Layer
Mucosa Layer of Esophagus
epithelium is nonkeratinized (mucosal) stratified squamous epithelium
abrasion-resistant
Muscularis Mucosae
- thin/absent in pharynx
- thickens to 200-400um in esophagus
- found in submucosa layer
- single layer of longitudinal smooth muscle
Submucosal Glands
in digestive system, only found in Duodenum and Esophagus
simple, branched, tubular glands that produce mucous secretion that lubricated the bolus + protects epithelial surface
Submucosa Layer of Esophagus
contains Muscularis Mucosae and Submucosal Glands
Muscular Layer of Esophagus
-has inner + outer longitudinal layer; covered in Adventitia of connective tissue
- in superior third, both contain mostly skeletal muscles
- in middle third, even mixture of skeletal + smooth muscles
- in inferior third, contains only smooth muscles
Adventitia of Esophagus
outside of muscular layer of esophagus
-anchors esophagus to posterior body wall
RetroPeritoneum of Esophagus
peritoneum covers anterior and left lateral surface
- only found on esophagus that is between diaphragm and stomach
Blood Vessels that supply Esophagus (7)
1 esophageal artery 2 thyrocervical trunk 3 external carotid arteries of neck 4 bronchial arteries 5 esophageal arteries of mediastinum 6 inferior phrenic artery 7 left gastric artery of abdomen
Intraperitoneal
Organs enveloped by visceral peritoneum
Retroperitoneal
Organs only covered by parietal peritoneum anteriorly
PRIMARY - organs that develop + remain outside of peritoneum
SECONDARY - organs originally intraperitoneal and then became retroperitoneal
SAD PUCKER
mnemonic for retropineal organs
S = Suprarenal (adrenal) Glands A = Aorta/IVC D =Duodenum (except the proximal 2cm, the duodenal cap) P = Pancreas (except the tail) U = Ureters C = Colon (ascending and descending parts) K = Kidneys E = (O)esophagus R = Rectum
MESENTERY
double layer of visceral peritoneum
- usually connects intraperitoneal organs to posterior wall
- provives pathway for nerves, vessels, lymphatics from body wall to viscera
4 Regions of the Stomach
1 CARDIA
2 FUNDUS
3 BODY
4 PLYORIC PART
CARDIA
most superior, medial portion of stomach
immediately surrounding the junction of the esophagus
Esophageal lumen opens into the Cardia of CArdiac Orifice
FUNDUS
region that projects superior to the junction b/w esophagus and stomach
contracts the inferior + posterior portion of the diaphragm
BODY of Stomach
area b/w Fundus and curve of J.
largest region of stomach
functions as a mixing tank for ingested food and gastric secretions
PLYORIC PART
“gatekeeper”
b/w body of stomach and duodenum
3 parts:
1 PYLORIC ANTRUM - connected to body
2 PYLORUS - muscular tissue surrounding pyloric orifice
3 PYLORIC SPHINCTER - regulates the release chyme into the duodenum
GASTRIC FOLDS
appears when stomach is empty of food and chime.
gradually flatens out until maximum distension
Blood Supply to Stomach
3 branches of the Celiac Trunk supply blood to the stomach:
1 Left gastric artery - supplies lesser curvature and cardia
2 Splenic artery - supplies fundus
3 Left gastro epiploic artery - supplies greater curvature
4 Common hepatic artery (branches into 4a right gastric artery, 4b right gastro epiploic artery, 4c gastroduodenal artery) - supplies greater + lesser curvatures at the plyrosus
5 Gastric vein + Gastro epiploic vein - drain blood intoHepatic portal vein
Musculature of Stomach
muscularis mucosae + muscular layer of stomach has extra layers of smooth muscle (normally it is just circular and longitudinal layers).
extra layers strengthen the stomach wall, assist in mixing + churning the chyme
muscularis mucosae contain an outer circular layer
muscular layer has inner oblique layer
Omenta
mesenteries of the stomach
connects stomach to adjacent organts
Greater omentum - large pouch that is more inferior, attached to greater curvature
Lesser omentum - superior, attached to liver + first segment of duodenum, and lesser curvature
Layers of Stomach Wall
surface epithelium of gastric mucosa is simple columnar epithelium composed of mucous surface cells
produces layer of mucus that covers the luminal surface of somach
protects the epithelium against acids and enzymes
Gastric Pits
shallow depressions that open onto gastric surface pit
the base of pits contains regenerative stem cells that actively replace the cells that are continuously sheding into chyme
also protects superficial epithelial cells if damaged from stomach acid or digestive enzymes
4 Gastric Secretory Cells
Mucous Neck Cells
Parietal Cells
Enteroendocrine Cells + G Cells
Chief Cells
Gastric Juice
made by Parietal Cells + Chief Cells
Mucous Neck Cells
- found in call regions of stomach
- columnar in shape
- apical cytoplasm is filled w secretory product that is water-solulable + lubricates stomach contents
Parietal Cells
- large round/pyramid shaped
- numerous in the proximal portion of gastric glands
- secretes Intrinsic Factor + Hydrochloric Acid (HCl)
Intrinsic Factor
glycoprotein that helps absorb vitamin B12 across intestinal lining
secreted by Parietal cells
Hydrochloric Acid (HCl)
lowers the pH of gastric juice,
kills microorganisms,
breaks down plant cell walls, connective tissues in meat, + denatures protein
secreted by Parietal cells
Enteroendocrine Cells + G Cells
Enteroendocrine - numerous in Fundus, occasionally found in Cardia + Pyloric Part
-scattered among chief cells + parietal cells
G Cells
- type of enteroendocrine cells found in Gastric Pits of Pyloric Part
- secretes Gastrin when food enters stomach
Gastrin
-secreted by G cells
- stimulates the secretory activity of both parietal + chief cells
- promotes smooth muscle activity in the stomach wall to enhance churning + mixing activity
Chief Cells
- found only in Funduss
- most abundant in base of gastric gland
- secretes Pepsinogen which turns into Pepsin
in newborns, produces Rennin + Gastric Lipase (enzymes vital for milk digestion)
Pepsinogen
- inactive proenzyme
- activated when come in contact w acid in the gastric lumen (turns into Pepsin)
Pepsin
- active proteolytic (protein digesting enzyme)
- functions most effectively in pH of 1.5-2.0
Rennin + Gastric Lipase
Rennin coagulates milk protein
Gastric Lipase initiates digestion of milk fats
both produced by Chief cells in Fundus
Regulation of Gastric Activity
directly by CNS - vagus nerve (sight/thought of food
triggers parasympathetic to innervate parietal, chief, + mucous cells of stomach); branches of celiac plexus (sympathetic inhibits)
indirectly by Local Hormones - small intestines release 2 hormones that inhibits gastric secretion:
Secretin
Cholecytokinin
Secretin + Cholecytokinin
stimulate secretioin by both pancreas and liver
also depresses the gastric activity
Small intestines
- 90% of absorption
- found in all abdominal regions except left hypochondriac + epigastric region
- held by mesentaries attached to wall
3 Subdivisions of Small Intestines
1 Duodenum
2 Jejunum
3 Ileum
Duodenum
- shortest + widest
- connected to Pylorus of Stomach
- mixing bowl of chyme fr stomach, + digestive secretions of liver + pancreas
- ring of smooth muscle regulates movement of chyme
Jejunum
- second segment starts at Duodenojejunal flexure
- re-enters the peritoneal cavity becoming intraperitoneal
- bulk of digestion + nutrient absorption
- typically found in umbilical region
Ileum
- longest segment of small intestine that is intraperitoneal proximally, then secondary retroperitoneal in the rest
- typically in hypogastric region
- mesentary has more fat, is thicker
Mesentery Proper
- fan shaped mesentary that covers jejunum and ileum
Histology of Digestive Tract
Mucosa Muscularis Mucosae Submucosa Muscular layer Serosa
Intestinal Epithelium
1 Circular Folds -large flaps in mucosa
2 Intestinal Villi - fingerlike projection of mucosa
3 Microvilli - the columnar cells that cover the Intestinal Villi
increases the surface area of small intestines
increases the surface
Intestinal Gland
- glandular pockets that extend deep into underlying lamina propria
- at the base, stem cells continuously divide to produce new epithelial cells (old cells turn into intracellular chyme)
Paneth Cells
- at base of intestinal glands
- secretes DEFENSINS + LYSOZYME for innate (nonspecific) immunity (kills some bacteria but ignores good bacteria)
Lamina Propria of Intestinal Villi
loose areolar connection tissue located within the core of each villi
contains lymphatic cells, ocassional lymphoid nodules, extensive network of capillaries, LACTEAL,
Lacteal
found w/in Lamina Propria
lymphatic vessel that transports materials that cannot enter blood capillaries
Terminal Ileum
contains ileocecal sphincter - controls flow of chyme into large intestines
