chapter 28 structure and function of the gastrointestinal system
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Essentials of Pathophysiology. Chapter 28 Structure and Function of the Gastrointestinal System. The digestive tract is a single-layered tube. The gastrointestinal tract is innervated by both the sympathetic and parasympathetic nervous systems. - PowerPoint PPT PresentationTRANSCRIPT
PRE LECTURE QUIZ TRUE/FALSE
The digestive tract is a single-layered tube. The gastrointestinal tract is innervated by
both the sympathetic and parasympathetic nervous systems.
The gastrointestinal tract is the largest endocrine organ in the body.
Each day, approximately 7000 mL of fluid is secreted into the gastrointestinal tract.
Absorption is the process of moving nutrients and other materials from the external environment of the gastrointestinal tract into the internal environment.
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PRE LECTURE QUIZ The __________ is a tube that connects the
oropharynx with the stomach. The small intestine, which forms the middle
portion of the digestive tract, consists of three subdivisions: the duodenum, the jejunum, and the __________.
__________ movements are rhythmic propulsive movements that occur when the smooth muscle layer constricts, forming a contractile band that forces the intraluminal contents forward.
The __________ serves as a reservoir for ingested solids and liquids.
__________ is the process of dismantling foods into their constituent parts.
Digestion
Esophagus
Ileum
Peristaltic
stomach
THE JOB OF THE BOWEL
Food: Movement Breakdown Absorption
Keeping dangerous gut contents out of the blood
Keeping blood contents from being lost into the gut lumen
QUESTION
Tell whether the following statement is true or false.
The mesentery contains the intestine’s blood supply.
ANSWER
TrueAn extension of the visceral peritoneum,
the mesentery contains blood vessels that supply oxygen and nutrients to (arteries) and eliminate CO2 and waste from (veins) the intestines.
PRADER-WILLI SYNDROME
It is traditionally characterized by hypotonia, short stature, hyperphagia, obesity, behavioral issues (specifically OCD-like behaviors), small hands and feet, hypogonadism, and mild mental retardation.
Plasma ghrelin levels are extremely high
Discussion:
What are the effects of this disorder?
ghrelin a gastrointestinal hormone produced by epithelial cells lining the fundus of the stomach; appears to be a stimulant for appetite and feeding, but is also a strong stimulant of growth hormone secretion from the anterior pituitary
Ghrelin levels increase before meals and decrease after meals. It is considered the counterpart of the hormone leptin,
PRADER-WILLI SYNDROME
This is a picture of a child with Prader-Willi Syndrome, first with a small, undersized figure, then as an obese teenager later in life.
SCENARIO
A woman has a pancreatic tumor that secretes gastrin- a hormone that stimulates the secretion of gastric juice.
Question What complication is likely to
develop? Why?
CARBOHYDRATE DIGESTION
Mouth: Salivary amylase Duodenum: pancreatic amylase
Polysaccharides disaccharides Brush border enzymes
Disaccharides monosaccharides
Monsaccharides absorbed into blood
PROTEIN DIGESTION
Stomach: pepsinogen Activated to pepsin by acid in stomach Breaks proteins into polypeptides
Duodenum: pancreatic trypsinogen Activated to trypsin in duodenum Breaks proteins into polypeptides
Brush border enzymes Breaks polypeptides into 2–3 amino
acid peptides Peptides absorbed into blood
FAT DIGESTION
Duodenum: bile Emulsifies fats
Duodenum: pancreatic lipase Breaks triglycerides into glycerol and fatty
acids Jejunum
Packages digested fats as chylomicrons Passed to the lymph
QUESTION
Digestion of which substance begins in the mouth?
a. Carbohydratesb. Proteinc. Fat d. All of the above
ANSWER
a. CarbohydratesCarbohydrate digestion begins in the
mouth with salivary amylase; protein digestion begins in the stomach with pepsinogen; fat digestion begins in the small intestine with bile and pancreatic lipase.
DISCUSSION
Which is the best choice to reduce fat digestion?
Suppress duodenal hormone secretion
Suppress the activity of chief cells in the stomach
Decrease intrinsic factor secretion
Block gall bladder contraction
Inactivate pancreatic lipase
QUESTION
How would fat digestion be affected if bile levels decreased?
a. It would increase.b. It would decrease.c. It would have no effect—fat digestion
is mainly affected by amylase.d. It would have no effect—fat digestion
is mainly affected by lipase.