AnP Chapter 21 (LO5) Flashcards
The digestive tract includes
Mouth Pharynx Esophagus Stomach Small and large intestine Rectum Anus
The accessory organs of digestive tract
Teeth Tongue Salivary glands Liver Pancreas gallbladder
digestion
breaks down food and transforms it into a substance that cells can use
mechanical digestion
this is the first stage of digestion
involves physically breaking down food into smaller pieces beginning with chewing and continuing with contractions and churning in stomach and small intestine
chemical digestion
the second phase of digestion uses digestive enzymes produced in the salivary glands, stomach, pancreas and small intestines to break down food particles into nutrients that cells can use
Four layers of tissue make up the walls of the digestive tract
the mucosa,
the submucosa,
the muscularis
the serosa
The mucosa
innermost layer
Consists of 3 layers of its own
Secretes mucus, digestive enzymes and hormones
Absorbs nutrients after digestion
Contains lymphoid tissue that protects against disease
The submucosa
thicker layer of connective tissue that contains glands, blood vessels, lymphatic vessels and nerves
the muscularis
consists of two layers of smooth muscle
contracts and relaxes to propel food
the serosa
outer most layer; covers portion of digestive tract
enteric nervous system (ENS)
the digestive system’s nervous system
consist of 500 million neurons
part of the ANS and regulates digestive motility, secretion and blood flow
myentreric nerve plexus:
resides between the longitudinal and circular layers of muscle in the muscularis layer and submucosal nerve plexus
submucosal nerve plexus
which is embedded in the submucosa
Mesenteries
layers of visceral peritoneum that suspend the digestive organs within the abdominal cavity while anchoring them loosely to the abdominal wall
Contain blood vessels, nerves, lymphatic vessels and lymph nodes that supply the digestive tract
Ascites
accumulation of fluid in the peritoneal cavity
Greater omentum
a portion of the mesentery extending from the greater curvature of the stomach and hanging down over the small intestines
Prevents friction and helps localized infection
Lesser omentum
extends from the lesser curve of the stomach to the liver
Mesocolon
fixes the colon to the posterior abdominal wall
Mouth
Where digestion begins
Hard palate
form by the portions of the maxilla and palatine bones; separates the mouth from the nasal cavity
Soft palate
which consist of mostly skeletal muscle it forms an arch between the mouth and the nasopharynx
Uvula
a cone shaped process that hangs down from the soft palate
Tongue
a skeletal muscle covered buy a mucous membrane it repositions food in the mouth during chewing it also contains taste buds
Lingual frenulum
a fold a mucous membrane that anchors the tongue to the floor of the mouth
Saliva
a clear fluid consisting mostly of water but also containing mucus, an enzyme that kills bacteria, antibacterial compounds, electrolytes and two digestive enzymes secreted by salivary gland’s
The parotid gland
but it’s just underneath the skin anterior to the ear it drains saliva to an area near the second upper molar
The submandibular gland
empties into the mouth on either side of the lingual frenulum
The sublingual gland
drains through multiple ducts onto the floor of the mouth
Mastication
digestion begins when food enters the mouth and he’s chewed
Teeth
The adult mouth contains 32 permanent teeth
Incisors
chisel like sharp edges for cutting food
Canine
pointed teeth design to tear food
Premolars and molars
have large flat surfaces for crashing or grinding
The crown
the portion of the tooth above the gum
Neck
a location where the route and crown meet the gumline
Root
it’s in bedded into a socket in the jawbone
Enamel
hard tissue that covers the crown
Dentin
firm yellowish tissue that is contained in the bulk of the tooth
Pulp cavity
contains a mass of connective tissue, blood and lymph Fattic vessels, and nerves called pulp
Pulp fills the root canals of each root
Periodontal ligament
Lines of socket fibers from ligament infiltrate both route and socket to anchor the tooth in place
Cementum
connective tissue that covers the Dentin in the root
Pharynx
After food leaves the oral cavity it moves into the pharynx
- After food has been broken down by the teeth and moistened by saliva the tongue manipulates the bolus to the back of the oral cavity
- At this point the soft palate lifts while the larynx rises and food moves through the oropharynx and laryngopharynx on its way to the esophagus
Esophagus
a muscular tube about 10 inches that connects the pharynx to the stomach
Lower esophageal sphincter
muscular sphincter helps prevent backflow of stomach acid into the esophagus
Peristalsis
a wave like muscular contraction that propels the food toward the stomach
stomach
sac that stores food
Chyme
semi fluid mixture that leaves the stomach and enters the duodenum by passing through pyloric sphincter
Lesser curvature
Greater curvature
along the upper surface of the stomach
Stomachs 4 regions
cardia, fundus, body and pylorus
Parietal cells
secrete hydrochloric acid which helps kill microbes in swallowed food and intrinsic factor
Chief cells
secrete digestive enzymes such as Pepsinogen
Enteroendocrine cells
secrete the hormone ghrelin (which stimulates the hypothalamus to increase appetite) and gastrin ( which influences digestive function
Liver
Body’s largest gland fills the upper right abdomen below the diaphragm
Performs more than 250 tasks including storing and releasing glucose, processing vitamins and minerals, filtering toxins and recycling old blood cells
Liver has four lobes two
Lobes (the right and left) are visible from an anterior view
Term hepatic refers to the liver
Hepatitis is swelling and inflammation of the liver
The caudate lobe:
The quadrate lobe:
The caudate lobe: near the inferior vena cava
The quadrate lobe: next to the gallbladder
Heptic artery
oxygenated blood from the aorta to the liver
Portal vein
carries oxygenated poor but nutrient rich blood from the digestive organs and spleen to liver
Haptic lobules
tiny six sided cylinders that fill the interior of the liver and or the functional unit of the liver
Central vein
passes through the core of each lobule
Hepatocytes
sheets of hectic cells found out from the center of the lobule
Sinusoids
passageways filled with blood
Blood flow through the liver
- Nutrient rich blood from stomach and intestines enter the lobule through small branches of the portal vein
- Oxygen rich blood enters the lobule through small branches of the heptic artery
- The blood filters through the sinusoids allowing cells to remove nutrients as well as hormones, toxins and drugs
- —At the same time the liver secrete substances into blood for distribution throughout the body - Also phagocytic cells called Kupffer cells remove bacteria, worn out red blood cells and debris from bloodstream
- The central vein carries the processed blood out of the liver
- Canaliculi: Carry bile secreted by hepatic cells and ultimately drain into the right and left hepatic ducts
Gallbladder
A sac attached to the underside of the liver it stores and concentrates bile
Bile reaches the gallbladder through a series of ducks it leaves delivered by the right and left haptic ducks which converge to form the common haptic duct and goes on to become the common bile duct
—Bile from the liver first fills the common bile duct before backing up into the gallbladder through the cystic duct
Hepatopancreatic ampulla
formed by the bile duct merged with the duct of the pancreas
Major duodenal papilla
raised area that the ampulla enters the duodenum
Hepatopancreatic sphincter
sphincter that controls the flow of bile and pancreatic juice into the duodenum
Pancreas
Lies behind the stomach
Both an endocrine and exocrine gland
It’s in the crane function centres on pancreatic isolate that secrete insulin and glucagon
Most of the pancreas consists of exocrine tissue
Acinar cells
Secrete digestive enzymes in an in active form once activated the enzymes help break down lipids, proteins and carbohydrates
Small intestine
Where most chemical digestion and most nutrient absorption occurs
Consists of three divisions: the duodenum, the jejunum and ilium
The duodenum
the first 10 inches of small intestine it begins at the pyloric valve and ends as the intestine turns abruptly downward
Receives chyme from the stomach as well as pancreatic juice and bile
This is where stomach acid is neutralized and pancreatic enzymes begin the task of chemical digestion
The jejunum
constitutes the next 8 feet of the small intestine it has many large closely spaced folds and millions of microscopic projections which gives it an enormous surface area
Ideal location for nutrient absorption
The wall is thick and muscular with a rich blood supply
The ileum
the last 12 feet of intestine the wall is thinner and has less blood supply
Peyer’s patches: cluster of lymphatic nodules that are scattered throughout
Circular folds
contained in the intestinal lining and slows the progress of time and increase its contact with mucosa
Lacteal
an arteriole, a venule and a lymph vessel that fill the core of each villus
Covering the villi are absorptive epithelial cells as well as mucous secreting goblet cells
The mucus after being secreted by the goblet cells expands to create a dense layer attached to the epithelium that is impenetrable to bacteria
Intestinal crypts
pores at the base of the villi that contain goblet cells that secrete mucus that helps the passage of food
Serve as sites for rapid cellular growth producing new cells to replace those shed from villi
Carbohydrates
Carbohydrates consist of sugars called saccharides
Polysaccharide
contain many Saccharide groups linked together these include starches and glycogen
Disaccharide:
contain two groups linked together these include sucrose lactose and Maltose
Monosaccharide
contain only one saccharide group please include glucose, fructose and galactose
how are polysaccharides broken into smaller particles (disaccharides and monosaccharides) by digestive enzymes
- Carbohydrate digestion begins in the mouth were salivary gland secretes the enzyme amylase
- –Salivary amylase works to hydrolyze polysaccharides into disaccharides - What is the food is swallowed a low pH of stomach acid in activates the salivary amylase
- –By this point about 50% of the starch has already been digested - When the resultant chyme reaches the small intestine it mixes with pancreatic amylase and the process of starch digestion resumes
- The final steps take place at the level of the villi
—The membranes of the epithelial cells covering the villi contain enzymes sucrase, lactase and maltase
—As the chyme slides against the brush border of the epithelial cells the enzymes bind with the disaccharides
The final step produces glucose which is immediately absorbed
Protein
Complex molecules consisting of folded and twisted chains of amino acids linked together by peptide bonds
how break down of protein works
- The stomach, the enzyme pepsin hydrolyzes the peptide bonds between certain amino acids
- As soon as the chyme enters the duodenum pepsin is an activated
- –At that point the pancreatic enzymes tryspin and chymotrypsin assume the task of breaking the peptide bonds - Finally brush border enzymes called peptidases Break the remaining chains into individual amino acids which are then absorbed into the bloodstream
Fats
Fat digestion begins in the mouth with the secretion of the enzyme lipase
Most fat digestion however occurs in the small intestine
To facilitate digestion the fat must be broken into smaller droplets a process called emulsification
Large intestine
Once the food has been processed and its nutrients absorbed the remaining residue is ready to leave the small intestine for the large intestine
The large intestine absorbs large amounts of water from residue before passing the resulting waste material faeces out of the body
All along the colon are Pouches call haustra which result from the increased tone of the smooth muscle of muscularis layer
how the large intestine works
- The large intestine begins in a blind pouch called the cecum
- –Attached to the lower end of the cecum is the appendix which contains masses of lymphoid tissue and serves as a source for immune cells
- –The point where the ileum meets the large intestine is the ileocecal valve which helps insure that material moves in a forward direction only - The ascending colon extends up toward deliver the colon makes a sharp turn at the right colic (hepatic) flexure
- The transverse colon passes below the liver, stomach and spleen the colon turn sharply downward at the left colic (splenic) flexure
- The descending colon extends downward along the left side of the abdominal cavity
- Sigmoid colon forms and S shape down to the rectum
- The rectum is the last 7 to 8 inches of intestine
- Anal canal which makes up the last inch of the rectum opens to the exterior through the anus
- –The anus contains two sphincters and internal sphincter composed of involuntary smooth muscle and an external sphincter composed of voluntary skeletal muscles
Key digestive enzymes
- state enzyme (s) and substance digested
salivary glands
enzyme
- Amylase
- Lipase
substance digested
- Starch
- Fat
Key digestive enzymes
- state enzyme (s) and substance digested
stomach
enzyme
-pepsin
substance digested
- protein
Key digestive enzymes
- state enzyme (s) and substance digested
pancreas
enzyme
- Proteases (tryspin, chymotrypsin)
- Lipase
- Amylase
substance digested
- Protein
- Fats
- Starch
Intestine
enzyme
- Peptidases
- Sucrase
- Lactase
- Maltase
Peptides
- Sucrose (cane sugar)
- Lactose (milk sugar)
- Maltose (malt sugar)
