***Ch 24 Digestive System *** A&P II
Absorption of Amino acids, dipeptides and tripeptides
Most are absorbed as amino acids via active transport into the blood ½ of absorbed AA come from proteins in digestive juice and dead mucosal cells
Enteric nervous system (ENS)
Neurons extending from esophagus to anus with 2 plexuses
Which of the following small intestine cells secrete lysozyme? Mucosa cells Paneth cells S cells Goblet cells Absorptive cells
Paneth cells
Which of the following cells secrete hydrochloric acid? Parietal cells Serosa cells Chyme cells Mucous cells Chief cells
Parietal cells
Circular folds
Permanent folds (~1 cm deep) that force chyme to slowly spiral through lumen, allowing more time for nutrient absorption
Mucosa
The innermost layer of the human digestive tract; in some parts of the digestive system, it contains mucus-secreting cells and glands that secrete digestive enzymes
Large intestine overall function
complete absorption, produce certain vitamins, and form and expel feces
Muscularis of GI tract
composed of circular fibers and longitudinal fibers which is responsible for segmental contractions and peristaltic movement
bile salts
compounds in bile that aid in emulsification
pancreatic duct function
conducts pancreatic juice from the pancreas to the small intestine
Lamina propria digestion
connective tissue with blood and lymphatic vessels it is modified to allow the passage of a large number of ducts, which connect to the liver, pancreas, and salivary glands.
visceral peritoneum
covers organs also called the Serosa
what is the series of hollow organs joined in a long, twisting tube from the mouth to the anus—and other organs that help the body break down and absorb food
digestive tract
Microvilli in intestines
fingerlike extensions for increasing surface area for absorption/secretion of intestinal juice
Duodenum
first part of the small intestine
duodenum
first part of the small intestine
Hepatopancreatic duct
fusion of common bile duct and pancreatic duct into duodenum
which cell functions to store and concentrate bile produced by the liver until it is needed in the small intestine
gallbladder
large intestine
in all animals water is absorbed, bacterial fermentation takes place, and feces are formed
Sympathetic in digestion
inhibits digestion, don't want energy to go to digestion while running from bear
mucosa of GI tract
inner epithelial lining, it is the soft tissue that lines the body's canals and organs in the digestive, respiratory and reproductive systems which functions in absorption and secretion
what enzyme digests lipids?
lipase
_____is the heaviest gland of the body
liver
which organ is critical to the digestion and absorption of fats
liver
Hepatocytes
liver cells that produce bile
antrum of stomach
lower portion of the stomach
body of stomach
main central region of stomach
mixing waves
mix the stomach contents with stomach secretions to form chyme
Organs of the digestive system
mouth, pharynx, esophagus, stomach, small intestine, large intestine
MALT
mucosa associated lymphoid tissue; protects against ingested microbes
Myenteric plexus
nerve supply between the two layers of the muscularis externa; provides smooth, coordinated contraction for peristalsis
Serosa of GI tract
outer layer of connective tissue covered with visceral peritoneum which mostly composed of connective tissue and gives strength to the long digestive tract, attaching itself to surrounding structures.
which organ is critical for the digestion of fats, carbohydrates and protein?
pancreas
Which major duct carries a fluid rich in bicarbonate ions?
pancreatic duct
what enzyme digests proteins?
pepsin
In the mouth, the tooth sockets are lined with
periodontal ligament
gastric phase
phase of gastric secretion that begins when food enters the stomach
Bilirubin function
pigment released by the liver in bile, functioning to help liver break down food. It is a yellowish substance made during your body's normal process of breaking down old red blood cells
descending colon
portion of the colon that extends downward from the transverse colon
Which of the following is the forerunner of the gastrointestinal tract? foregut endoderm primitive gut midgut hindgut
primitive gut
smooth muscle in digestion
produces a forceful contractions that produce muscle shortening to propel the bolus along the gastrointestinal tract.
villi of small intestine
provide an enormous surface area that facilitates absorption.
rectum
A short tube at the end of the large intestine where waste material is compressed into a solid form before being eliminated
Esophagus
A simple conduit between the mouth and stomach
bolus
A soft mass of chewed food.
bile duct
A tube that carries bile from the liver and gallbladder to the intestine
Which of the following are the primary function(s) of the large intestine? A. Chemical digestion B. Absorption C. Feces formation D. Regulation of blood glucose
A, B & C
Which of the following are a function(s) of the liver? A.) Conversion of carbohydrates B.) Protein metabolism C.) Storage of bilirubin D.) Phagocytosis E.) Storage of vitamins
A, B, D & E
Which of the following processes is the primary function of the villi of the small intestine? Ingestion Secretion Mixing and propulsion Absorption None of these choices
Absorption
absorption of monosaccharides
All dietary carbohydrates digested are absorbed by facilitated diffusion or active transport into blood leaving only indigestible cellulose fibers left in feces
chief cells cells of stomach
epithelial cells in the gastric glands in the stomach lining. They are responsible for the secretion of pepsinogen and gastric lipase.
anal canal
region, containing two sphincters, through which feces are expelled from the body
pyloric sphincter
ring of muscle that guards the opening between the stomach and the duodenum (small intestine)
Sublingual gland
salivary gland under the tongue, smallest
Partoid gland
salivary gland within the cheek, just anterior to the ear
What is the enzyme present in saliva that breaks down fats?
salivary lipase
parietal cells of stomach
secrete HCl and intrinsic factor
chief cells
secrete pepsinogen and gastric lipase
Pepsin
secreted by chief cells, it's an Enzyme that breaks down proteins in the stomach
Parasympathetic in digestion
stimulates digestion, remember "rest and digest"
Chyme is created in the ________.
stomach
fundus function
stores undigested food and also the gases released from the chemical digestion of food
What organ breaks down food mechanically?
teeth in mastication
acessory digestive organs
teeth, tongue, salivary glands, liver, gallbladder, pancreas
Cecum
the cavity in which the large intestine begins and into which the ileum opens
Pancreatic juice
the clear alkaline digestive fluid secreted by the pancreas.
digestion of lipids in small intestine
Bile is secreted by the gallbladder to emulsify fat molecules and converts them into smaller fat droplets Pancreatic lipase breaks down small fat droplets into glycerol or monoglycerides.
cardia stomach function
Food and liquids pass through the cardia to enter the stomach from the esophagus. A valve near the cardia helps keep stomach contents from backing up into the esophagus
Mouth
Food is broken down mechanically by chewing and saliva is added as a lubricant. Saliva contains amylase, an enzyme that digests starch
saliva makeup
99.5% water, 0.5% solutes - uric acid, mucus,immunoglobulin A, lysozyme, and salivary amylase (acts on starch)
Submucosal Plexus
(plexus of Meissner) nerve supply that regulates the activity of glands and smooth muscle, aka secretions
Submucosa of GI tract
- areolar (loose) connective tissue - rich supply of nerves, blood and lymphatic vessels, and lymphoid follicles - abundant elastin and collagen
absorption of water
-9 L water, most from GI tract secretions, enter small intestine -95% absorbed in the small intestine by osmosis -Most of rest absorbed in large intestine -Net osmosis occurs if concentration gradient established by active transport of solutes -Water uptake coupled with solute uptake
muscles of the GI tract
-Purpose of these muscles are to mix food and ensure efficient digestion and absorption of nutrients
4 main regions of the stomach
1. Cardia 2. Fundus 3. Body 4. Pylorus
Enzyme activity and pH
Changing the pH will alter the charge and shape of the enzyme, which in turn will diminish its ability to bind the substrate, and help break down food
Which hormone is stimulated by high levels of dietary fat in the small intestine? Amylase Pepsin Secretin Gastrin Cholecystokinin
Cholecystokinin
Absorption of Lipids
Digestion begins in the small intestine (duodenum) and is complete by the end of the small intestine. Digestion of lipids CANNOT begin prior to their reaching the small intestine where the encounter bile and lipase. Triglycerides are broken down to fatty acids, transported across them membrane, then reformed into triglycerides. Enter at the LACTEALS. In order for lipids to travel in blood and lymph, they must 1) bind to a carrier protein (albumin) or 2) be formed into a chylomicron or micelle.
Cystic duct
Duct leading from the gallbladder to the common bile duct; carries bile
Role and composition of bile
Each day, hepatocytes secrete 800-1000 mL (about 1 qt) of bile, a yellow, brownish, or olive-green liquid. It has a pH of 7.6-8.6 consists mostly of water, bile salts, cholesterol, a phospholipid called lecithin, bile pigments, and several ions. principal bile pigment is bilirubin
Which of the following accessory organs stores bile? Pharynx Teeth Gallbladder Salivary glands Liver
Gallbladder
where are the liver's digestive juices stored?
Gallbladder
pepsinogen and gastric lipase do what?
Gastric lipases are responsible for the digestion of exogenous lipid Pepsinogen is initially activated by the H+ ions. The activated enzyme then acts autocatalytically to increase the rate of formation of more pepsin which breaks down proteins in food during digestion.
stomach acid
HCl, Breaks down proteins, breaks them down into sugar and acids
Which type of hepatitis is spread via fecal contamination of objects such as food, clothing, toys, and eating utensils and is characterized by loss of appetite, malaise, nausea, diarrhea, fever, and chills. Hepatitis C Hepatitis A Hepatitis D Hepatitis B Hepatitis E
Hepatitis A
periodontal ligament
Holds tooth in the socket
Peristalsis
Involuntary waves of muscle contraction that keep food moving along in one direction through the digestive system.
Chyme function
It increases the surface area of food by breaking it down into smaller components. It also stimulates digestive glands (gallbladder and pancreas) to secrete their respective solutions (bile, digestive enzymes, and bicarbonate)
Which of the following pancreatic enzymes digests lipids? Trypsin Elastase Lipase Pepsin All of these choices
Lipase
Which of the following accessory organs produces a fluid that functions to emulsify dietary fats? Gallbladder Pharynx Teeth Liver Salivary glands
Liver
what organ provides bile salts to the small intestine, which are critical for the digestion and absorption of fat?
Liver
Solid digestive organs
Liver and Pancreas
Which structure is composed of prominent lymphatic nodules that function in the immune response? Submucosa Mucosa Lamina propria MALT Serosa
MALT
Which layer functions by secreting a lubricating fluid? Mucosa Muscularis Muscularis MALT Serosa
Mucosa
what are the muscles of the GI tract?
Muscularis: The muscularis consists of two smooth muscle layers, a thin outer longitudinal layer that shortens and elongates the gut, and a thicker inner circular layer of smooth muscle, which causes constriction.
Which plexus is located between the longitudinal and circular smooth muscle layers of the muscularis?
Myenteric plexus
2 plexuses of the ENS
Myenteric plexus - GI tract motility Submucosal plexus - controlling secretions
Digestion of Nucleic acids
Ribonuclease and deoxyribonuclease in pancreatic juice---RNA and DNA broken down into nucleic acids
Which structure of the stomach allows greater distension for food storage? Sphincter Pylorus Rugae Cardia Fundus
Rugae
Which of the following accessory organs produces a fluid to soften food? Salivary glands Teeth Liver Gallbladder Pharynx
Salivary glands
Brunner's glands Secrete an acidic juice Secrete an acidic mucus Secrete an alkaline juice Secrete an alkaline mucus
Secrete an alkaline mucus
mucosa epithelium
Simple columnar with many goblet cells that secrete mucus to ease passage of food down the tract.
where are almost all nutrients are absorbed?
Small intestine
cementum
Specialized, calcified connective tissue that covers the anatomic root of a tooth.
Which of the following is NOT a function of the liver? Storage of vitamins Storage of bilirubin Conversion of carbohydrates Phagocytosis Protein metabolism
Storage of bilirubin
Gastric lipase
enzyme to digest fat, secreted by chief cells
True or False? The pancreas is Important as both an endocrine and exocrine organ.
True, As an exocrine gland, it secretes pancreatic fluid that contains bicarbonate and digestive enzyme And it also produces hormones in its 'endocrine' cells which monitor what is happening in the blood. They then can release hormones directly into the blood when necessary.
Why is digestion important?
We must break down the food we eat into smaller molecules that can be absorbed and carried to cells of the body Digestion involves mixing food with digestive juices, moving it through the digestive tract, and breaking down large molecules of food into smaller molecules. • Digestion begins in the mouth, when you chew and swallow, and is completed in the small intestine.
Stomach
Where the real action begins - enzymatic digestion of proteins initiated and foodstuffs reduced to liquid form.
Hepatopancreatic duct function
a connection between areas of your digestive system. It acts as a reservoir for pancreatic juices and bile, enabling the release of these substances that help your body break down and absorb food
submandibular gland
a salivary gland inside the lower jaw on either side that produces most of the nocturnal saliva
4 regions of large intestine
1. cecum 2. colon 3. rectum 4. anal canal
Phases of digestion
1. cephalic phase 2. gastric phase 3. intestinal phase
Jejunum
Middle portion of the small intestine
Lingual glands
Minor salivary glands of the tongue that secrete salivary lipase-begins to digest fats (triglycerides)
After ____ hours chyme then exits the stomach via the pylorus and enters the duodenum of the small intestine
2 - 4 hours
How many stages of deglutition are there? 3 8 4 5 2
3
Muscularis
3rd layer made of 2 layers of smooth muscle that move food along the GI tract
6 functions of the digestive system
1. Ingestion 2. Mechanical processing 3. Digestion 4. Secretion 5. Absorption 6. Excretion
Layers of the GI tract
1. Mucosa 2. Submucosa 3. Muscularis 4. Serosa
Steps of stomach acid production
1. Water and CO2 combine to form carbonic acid. 2. H2CO3 dissociates. 3. H+ and bicarbonate ions are transported into the gastric lumen. 4. Cl- diffuses into the gastric 5. Chloride ion combines with H+ in the gastric lumen.
3 regions of small intestine
1. Duodenum 2. Jejunum 3. Ileum
2 groups of organs compose the digestive system
1. Gastrointestinal (GI) tract or alimentary canal 2. Accessory digestive organs
Which of the following is NOT a change in the digestive system associated with aging? Decreased secretory mechanisms Decreased motility of the digestive organs Loss of strength and tone of the muscular tissue Changes in neurosensory feedback regarding enzyme and hormone release All of these are age related changes in the digestive system
All of these are age related changes in the digestive system
identify the calcified connective tissue
B
Why do emotions such as anger or fear slow digestion? Because they stimulate the somatic nerves that supply the GI tract Because they stimulate the parasympathetic nerves supplying the GI tract They do not affect digestion Because they stimulate the sympathetic nerves that supply the GI tract Because all emotions are controlled by the Vagus nerve
Because they stimulate the sympathetic nerves that supply the GI tract
absorption of vitamins
Fat-soluble vitamins A, D, E, and K absorbed by simple diffusion and transported with lipids in micelles Most water-soluble vitamins also absorbed by simple diffusion
Which structure regulates the flow of material into the colon? Sigmoid colon Pyloric sphincter Anal canal Ileocecal sphincter Appendix
Ileocecal sphincter
Pancreas
Important roles as both an endocrine and exocrine organ - provides a potent mixture of digestive enzymes to the small intestine which are critical for digestion of fats, carbohydrates, and protein
hepatitis
Inflammation of the liver usually results from viruses, drugs and chemicals such as alcohol.
Which of following processes is the primary function of the mouth? Ingestion Secretion Mixing and propulsion Absorption None of these choices
Ingestion
Which portion of the peritoneum is largely responsible for carrying blood and lymph vessels to the intestines? Lesser omentum Mesentery Falciform ligament Mesocolon Greater omentum
Mesocolon
chemical digestion
Process by which enzymes break down food into small molecules that the body can use
Which of the following is NOT a primary function of the large intestine? Mechanical digestion Regulation of blood glucose Chemical digestion Feces formation Absorption
Regulation of blood glucose
Which of the following is a contribution of the digestive system to the muscular system? Small intestine absorbs dietary calcium and phosphorous salts. The liver can convert lactic acid to glucose. Small intestine absorbs vitamin D. Excess dietary calories are stored as triglycerides in adipose cells. The liver synthesizes most plasma proteins.
The liver can convert lactic acid to glucose.
Submucosal plexus vs Myenteric plexus
The myenteric plexus increases the tone of the gut and the velocity and intensity of contractions. The submucosal plexus is involved with local conditions and controls local secretion, absorption, and muscle movements.
Liver vs Pancreas
The pancreas produces digestive enzymes that help break down proteins, carbohydrates and fats. Liver. The liver produces bile, a solution that helps you digest fats
fundus of stomach
The upper left portion of the stomach, which has a curved, dome-shaped appearance.
Saliva contains _______, an enzyme that digests starch
amylase
What enzyme digests starch?
amylase
sigmoid colon
an S-shaped structure that continues from the descending colon above and joins with the rectum below
colon
another name for the large intestine
Cardia
area around the opening of the esophagus
why don't we eat our own stomach?
because it is lined with epithelial cells, which produce alkaline mucus. This forms a barrier between the lining of the stomach and the contents.
Digestion begins in the ____ and ends in the ______ _____?
begins in the mouth and ends in the small intestine
Amphipathic
bile salts have hydrophobic and hydrophilic regions—form micelles
small intestine does what?
breaks down the food mixture evenmore so your body can absorb all the vitamins,minerals, proteins, carbohydrates, and fats
Mixing and propulsion
churning and propulsion of food through the GI tract
Liver
the center of metabolic activity in the body - its major role in the digestive process is to provide bile salts to the small intestine, which are critical for digestion and absorption of fats.
cephalic phase
the earliest phase of digestion, in which the brain thinks about and prepares the digestive organs for the consumption of food
transverse colon
the middle part of the large intestine, passing across the abdomen from right to left below the stomach.
Small intestine
the most exciting place to be in the entire digestive system - this is where the final stages of chemical enzymatic digestion occur and where almost all nutrients are absorbed.
intestinal phase
the phase of gastric secretion that begins when chyme enters the intestine and moderates gastric activity through hormones and nervous reflexes
Ileum
third part of the small intestine
ascending colon
travels upward from the cecum to the undersurface of the liver
