DIGESTIVE SYSTEM: ANATOMY AND FUNCTIONS Flashcards
HOW LONG IS THE GI TRACT OF A HEALTHY ADULT?
9m
WHAT ARE THE SUPPORTING ORGANS OF THE GI TRACT?
SALIVARY GLANDS, LIVER, GALLBLADDER, PANCREAS
WHAT ARE THE MAIN ORGANS OF THE GI TRACT?
MOUTH, ESOPHAGUS, STOMACH, SMALL INTESTINE, LARGE INTESTINE
WHAT ARE THE PARTS OF THE SMALL INTESTINE?
DUODENUM (stomach exit), JEJUNUM, ILEUM
WHAT ARE THE PARTS OF THE LARGE INTESTINE?
CECEUM, ASCENDING COLON, TRANSVERSE COLON, DESCENDING COLON, RECTUM, ANUS
WHAT ARE THE LAYERS THAT LINE ALL PARTS OF THE GI TRACT EXCEPT FOR THE MOUTH CALLED?
THE MUCOSA, THE SUBMUCOSA, THE MUSCULARIS PROPRIA, THE SEROSA
IN WHICH LAYER OF THE GI TRACT DOES THE ABSORPTIVE FUNCTION OCCUR?
THE MUCOSA
WHAT IS THE STRUCTURE OF THE MUCOSA?
Single epithelial layer (inner layer facing the lumen made out of cells called enterocytes) attached to the lamina propria (connective tissue and lymph nodes) underneath which is the muscularis mucosae (smooth muscle cells)
WHAT TYPES OF CELLS DOES SUBMUCOSA CONTAIN?
INFLAMMATORY CELLS, AUTONOMOUS NERVE FIBERS AND GANGLION CELLS
WHAT DO THE GANGLION CELLS OF THE SUBMUCOSA DO?
CONTROL MUSCLE MOVEMENTS OF THE GI TRACT
WHAT ARE THE TWO LAYERS OF MUSCULARIS PROPRIA?
2 layers made out of smooth muscle cells:
- circualr (inner)
- longitudinal (outer)
HOW DOES MUSCULARIS PROPRIA PROPEL FOOD THROUGH THE GUT?
BY CONTRACTILE PERISTALTIC MECHANISMS WHICH ARE CONTROLLED BY THE MYENTERIC PLEXUS
WHAT IS THE ROLE OF SEROSA?
TO PROTECT THE GI TRACT FROM EXTERNAL AGGRESSIONS
DURING HUMAN EMBRYOGENESIS, WHEN DOES ESOPHAGUS DEVELOP?
AT 8-10 WEEKS
MUSCULARIS PROPRIA OF WHICH GI ORGAN IS THE ONLY ONE WHICH HAS BOTH SMOOTH AND STRIATED MUSCLES?
ESOPHAGUS
WHAT IS THE ESOPHAGEAL SEROSA CALLED?
ADVENTIA
HOW DOES ESOPHAGUS ENSURE ITS UNI-DIRECTIONAL FUNCTION?
- it has 2 sphincters (1st one stops the food from getting into trachea, the second one prevents stomach reflux)
- it generates peristaltic movements (reflex contractions of longitudinal and circular muscles)
WHAT IS CHYME?
SEMI LIQUID FLUID IN THE STOMACH AND SMALL INTESTINE
WHAT IS BOLUS?
CHEWED FOOD IN THE MOMENT OF SWALLOWING
WHAT IS FECES?
SEMI SOLID SUBSTANCE IN THE LARGE INTESTINE
PERISTALTIC REFLEX IS ALSO CALLED THE…
MYENTERIC REFLEX
WHICH PART OF NERVOUS SYSTEM CONTROLS THE MYENTERIC/PERISTALTIC REFLEX?
ENTERIC NERVOUS SYSTEM, REGULATED BY THE ANS
DOES PARASYMPATHETIC NERVOUS SYSTEM INCREASE OR INHIBIT PERISTALSIS?
IT INCREASES PERISTALSIS
PERISTALTIC REFLEX IS A COMBINATION OF WHICH TWO SEGMENTS AND WHAT ARE THEIR FUNCTIONS?
PROPULSIVE SEGMENT (constriction of the lumen and propulsion of the bolus) & RECEIVING SEGMENT (expansion of the lumen to receive the moving bolus)
WHEN DOES STOMACH DEVELOP DURING HUMAN EMBRYOGENESIS?
FROM 13 TO 39 WEEKS, BUT REGIONS PRESENT AT 14 WEEKS
WHAT IS THE NAME OF THE SPHINCTER THAT CONNECTS THE STOMACH AND DUODENUM?
PYLORIC SPHINCTER
ONE EXAMPLE OF STOMACH’S ENDOCRINE FUNCTION:
SECRETION OF HOROME GHRELIN WHICH REGULATES FOOD INTAKE
WHAT IS THE IMPORTANCE OF HCl SECRETION:
IT IS NECESSARY TO BREAK DOWN SECONDARY AND TERTIARY PROTEINS, TO KILL PATHOGENS AND TO ACTIVATE DIGESTIVE ENZYMES (e.g. PEPSINOGEN INTO PEPSIN)
WHAT IS THE ROLE OF SOMATOSTATIN IN THE GI SYSTEM?
IT REGULATES ACID PRODUCTION, REGULATES GLUCOSE LEVELS…
WHICH TYPES OF CELLS DO GASTRIC GLANDS IN THE MUCOSA CONSIST OF?
PARIETAL CELLS, NECK CELLS, PIT CELLS, CHIEF (ZYMOGENIC) CELLS AND ENDOCRINE CELLS
WHAT IS THE ROLE OF CHIEF (ZYMOGENIC) CELLS?
SECRETION OF DIGESTIVE ENZYMES (E.G. PEPSINOGEN, GASTRIC LIPASE AND AMYLASE)
WHAT IS THE ROLE OF NECK CELLS?
SECRETION OF BICARBONATE TO BUFFER THE pH
WHICH CELLS IN THE GASTRIC GLANDS IN THE MUCOSA PRODUCE HCl?
PARIETAL CELLS
WHAT IS THE STOMACH pH AT REST AND WHAT AFTER A MEAL?
4-5 AT REST, 1.5-3.5 AFTER A MEAL
MEALS HIGH IN WHICH OF THE MAIN NUTRIENTS REQUIRE A LOWER pH?
PROTEIN
WHAT PERCENTAGE OF CARBS ARE DIGESTED IN THE MOUTH?
5%
WHAT ARE AUTOANTIBODIES?
ANTIBODIES WHICH ATTACK OUR OWN BODY
WHAT DO EXCITATORY AND WHAT DO INHIBITORY MOTOR NEURONS RELEASE IN THE GI TRACT?
EXC: Ach and Substance P (induces contraction)
INH: NO and Vasoactive Intestinal Peptide (VIP) (induces relaxation)
WHEN THE BOLUS INDUCES A MECHANICAL STRETCH IN THE GUT WALL IT STIMULATES SECRETION OF WHAT FROM THE EPITHELIAL CELLS?
SEROTONIN (5HT)
WHAT DOES SEROTONIN DO IN THE GUT?
IT ACTIVATES SENSORY AFFERENT NEURONS OF THE MYENTERIC PLEXUS AND IT ALSO INHIBITS ITS OWN PRODUCTION IN THE EPITHELIUM (SO THERE AREN’T CONTINUOUS MOVEMENTS IN THE GUT EVEN WHEN THERE IS NO FOOD)
WHAT KIND OF STRUCTURES DOES THE MUCOSAL EPITHELIUM FORM AND WHAT ARE THEY CALLED?
FINGER-LIKE STRUCTURES, VILLI
WHICH PART OF THE GI TRACT DOES THE PERISTALTIC REFLEX START IN AND UP UNTIL WHICH POINT DOES IT CONTINUE?
STARTS IN THE ESOPHAGUS AND CONTINUES IN EVERY PART OF THE GI TRACT
HOW LONG IS THE SMALL INTESTINE?
7m