12a Abdomen Deep and the Digestive System Flashcards
The anus has two sphincters
- Internal anal sphincter composed of smooth muscle (involuntary-parasympathetic control)
- External anal sphincter composed of skeletal muscle (voluntary)
These sphincters are closed except during defecation
Colon
Has distinct regions: ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, and sigmoid colon
The transverse and sigmoid portions are anchored via mesenteries called mesocolons
95% of water is absorbed in the large intestines by osmosis
Large Intestines (Teniae coli)
three bands of longitudinal smooth muscle in its muscularis
Large Intestines (Haustra)
pocketlike sacs caused by the tone of the teniae coli
-Slow segmenting movements that move the contents of the colon and sequentially contract as they are stimulated by distension
Large Intestines (Epiploic appendages)
fat-filled pouches of visceral peritoneum
Parts of Colon
Ascending Colon
Transverse Colon
Descending Colon
Sigmoid Colon-S Curve to the rectum
Rectum and anal canal
Cecum with appendix
Sac that receives waste from the small intestines and lies below the ileocecal valve
Contains a worm-like vermiform appendix (lymphatic tissue)
Presence of food in the stomach
Activates the gastrocolic reflex
Initiates peristalsis that forces contents toward the rectum
The Gallbladder
Thin-walled, green muscular sac on the ventral surface of the liver
Stores and concentrates bile by absorbing its water and ions
Releases bile via the cystic duct, which flows into the bile duct
Composition of Bile
A yellow-green, alkaline solution containing bile salts, bile pigments, cholesterol, neutral fats, phospholipids, and electrolytes
The chief bile pigment is bilirubin, a waste product of heme
Bile salts
cholesterol derivatives that:
Emulsify fat
Facilitate fat and cholesterol absorption
Help solubilize cholestero
Enterohepatic circulation
recycles bile salts
The chief bile pigment is
bilirubin, a waste product of heme
Hepatocytes’ functions include
- Production of bile
- Processing bloodborne nutrients
- Storage of fat-soluble vitamins
- Detoxification
Secreted bile flows between hepatocytes toward the bile ducts in the portal triads
Liver sinusoids
enlarged, leaky capillaries located between hepatic plates
Kupffer cells
hepatic macrophages found in liver sinusoids
Portal Triads
Hexagonal-shaped liver lobules are the structural and functional units of the liver
Composed of hepatocyte (liver cell) plates radiating outward from a central vein
Portal triads are found at each of the six corners of each liver lobule
Portal triads consist of a bile duct and
Hepatic artery – supplies oxygen-rich blood to the liver
Hepatic portal vein – carries venous blood with nutrients from digestive viscera
The ligamentum teres
Is a remnant of the fetal umbilical vein
Runs along the free edge of the falciform ligament
The falciform ligament
Separates the right and left lobes anteriorly
Suspends the liver from the diaphragm and anterior abdominal wall
Exocrine function
Secretes pancreatic enzymes
1. Trypsin- polypetides>peptides
2. Lipase- fat>fatty acids
3. Amylase- Carbohydrates>glucose
4. Nucleases –Nucleic acid>nucleotides
5. Carboxypeptidase- polypeptides>peptides
Acini (clusters of secretory cells) contain zymogen granules with digestive enzymes
Endocrine function
- Insulin –(Beta cells of Islets of Langerhans) decreases blood sugar by removing it from blood into cells
2. Glucagon- (Alpha cells)increases blood sugar by breaking down glycogen into glucose and fat.
Cystic Duct
connect the Gall bladder to the Common Hepatic Duct to form the Common Bile Duct
Main Pancreatic Duct
also known as the Duct of Wursung
Accessory Pancreatic Duct
Duct of Santorini
Ampulla of Vater
Opening of the Main Pancreatic Duct
Sphincter of Oddi
Muscle that opens and closes the Ampulla of Vater.
Pancreas
Location
Lies deep to the greater curvature of the stomach
The head is encircled by the duodenum and the tail abuts the spleen
It produces the most digestive enzymes of any organs.(1200-15OO ml of digestive enzymes per day)
It is both a exocrine and endocrine gland
Small Intestine: Histology of the Wall
Cells of intestinal crypts (Crypts of Lieberkuhn) secrete intestinal juice
Peyer’s patches are found in the submucosa
Brunner’s glands in the duodenum secrete alkaline mucus (neutralizes the acidic `chyme from the stomach.
Microvilli (brush border cells)
tiny projections of absorptive mucosal cells’ plasma membranes and also secrete digestive enzymes
Villi
fingerlike extensions of the mucosa
Plicae circulares
deep circular folds of the mucosa and submucosa, force chyme to spiral through and increase the time of absorption.
Small Intestine: Gross Anatomy
Runs from pyloric sphincter to the ileocecal valve
Has three subdivisions:
1. Duodenum- 10-12 inches
2. Jejunum- 8 feet long
3. Ileum- 11 feet long
The jejunum extends from the duodenum to the ileum
The ileum joins the large intestine at the ileocecal valve
Stomach Ulcers
Caused by the bacteria Helicobacter pylori which burrs a hole through the mucosa and allows the HCl to further irritate the lining.
1. The bacteria secrete ammonia (base) that neutralizes the HCl
2. It then secretes a cytotoxin that damages the mucosal cells
3. It then produces proteins that separate the cells tight junctions
Stomach Lining
The stomach is exposed to the harshest conditions in the digestive tract
To keep from digesting itself, the stomach has a mucosal barrier with:
a. A thick coat of bicarbonate-rich mucus on the stomach wall
b. Epithelial cells that are joined by tight junctions
c. Gastric glands that have cells impermeable to HCl
Damaged epithelial cells are quickly replaced
Mucous neck cells
secrete acid mucus
Parietal cells
secrete HCl and intrinsic factor(needed for Vitamin B12 (nucleic acid metabolism and RBC maturation) absorption in Sm. Intestines)
Chief cells
produce pepsinogen
Pepsinogen is activated to pepsin by:
HCl the stomach
Pepsin breaks down proteins to polypeptides
Enteroendocrine cells – secretes
Gastrin-stimulates gastric glands (especially HCl) to increase there secretion, stimulates gastric emptying
B. Histamine-activates parietal cells to release HCl
C. Serotonin-stimulates gastric muscle contractions
D. Cholecystokinin (CCK)-allows pancreatic and bile enzymes to be released
E. Ghrelin-release when stomach is empty stimulating hunger and appetite.
Muscularis
has an additional oblique layer that:
a. Allows the stomach to churn, mix, and pummel food physically
b. Breaks down food into smaller fragments
Epithelial lining
Goblet cells that produce a double layer coat of alkaline insoluble mucus with bicarbonate in between.
Gastric pits
contain gastric glands that secrete gastric juice, mucus, and gastrin
Blood supply
celiac trunk (gastric artery), and corresponding veins (gastric veins) -part of the hepatic portal system
Nerve supply
sympathetic (vagus nerve)and parasympathetic fibers of the autonomic nervous system
Greater omentum
drapes inferiorly from the greater curvature to the small intestine and holds the intestines in place
Lesser omentum
runs from the liver to the lesser curvature
Lesser curvature
concave medial surface
Greater curvature
entire extent of the convex lateral surface
Pyloric region
made up of the antrum and canal which terminates at the pylorus
The pylorus is continuous with the duodenum through the pyloric sphincter
Body
midportion of the stomach
Fundus
dome-shaped region beneath the diaphragm
Cardiac region
surrounds the cardiac orifice and cardic shincter
Chemical breakdown of proteins begins and food is converted to
chyme
Hiatal Hernia
occurs when the cardiac (gastroesophageal) Sphyncter does not close when food is in the stomach.
-causes Pregnancy, Obesity, weak sphyncter
-the superior stomach can move up into the thoracic cavity.
Gastro Esophageal Reflux Disease (GERD)
is a the result with acid irritating the esophagus.
If chronic then esophageal cancer can result.
Esophageal Characteristics
Esophageal mucosa – nonkeratinized stratified squamous epithelium
The empty esophagus is folded longitudinally and flattened
Glands secrete mucus as a bolus moves through the esophagus
Muscularis changes from skeletal (superiorly) to smooth muscle (inferiorly)
Esophagus
Muscular tube going from the laryngopharynx to the stomach
Travels through the mediastinum and pierces the diaphragm
Joins the stomach at the cardiac orifice
Xerostomia
dry mouth
Sublingual gland
(mainly mucous)
Submandibular gland
equal serous and mucous
Parotid
only serous
Intrinsic salivary glands (buccal glands)
scattered throughout the oral mucosa
Three pairs of extrinsic glands
parotid, submandibular, and sublingual
Salivary gland Produces and secrete saliva
- Cleanses the mouth
- Moistens and dissolves food chemicals
- Aids in bolus formation
- Contains enzymes that break down starch
Sulcus terminalis
groove that separates the tongue into two areas:
Anterior 2/3 residing in the oral cavity
Posterior third residing in the oropharynx
Superior surface bears three types of papillae
- Filiform – give the tongue roughness and provide friction
- Fungiform – scattered widely over the tongue and give it a reddish hue
- Circumvallate – V-shaped row in back of tongue
Lingual frenulum
secures the tongue to the floor of the mouth and presents tongue from sliding posterior (if tight then the person becomes tongue tied (Ankloglossia)
Extrinsic muscles
alter the tongue’s position
Intrinsic muscles
change the shape of the tongue
Tongue
Occupies the floor of the mouth and fills the oral cavity when mouth is closed
Functions include:
1. Gripping and repositioning food during chewing
2. Mixing food with saliva and forming the bolus
3. Initiation of swallowing, and speech
Soft palate
mobile fold formed mostly of skeletal muscle
1. Closes off the nasopharynx during swallowing
2. Uvula projects downward from its free edge and assist food in downward projection
Hard palate
underlain by palatine bones and palatine processes of the maxillae
Assists the tongue in chewing by being a platform for food to be manipulated.
Slightly corrugated on either side of the raphe (midline ridge)
Labial frenulum
median fold that joins the internal aspect of each lip to the gum
Oral cavity proper
area that lies within the teeth and gums
Red Margin
apply lipstick and kisses
Myenteric nerve plexus
Major nerve supply that controls GI tract mobility
Submucosal nerve plexus
regulates glands and smooth muscle in the mucosa
Serosa
the protective visceral peritoneum
Replaced by the fibrous adventitia in the esophagus
Muscularis externa
responsible for segmentation and peristalsis
Submucosa
dense connective tissue containing elastic fibers, blood and lymphatic vessels, lymph nodes, and nerves
Muscularis mucosae
smooth muscle cells that produce local movements of mucosa
Lamina Propria
Loose areolar and reticular connective tissue
Nourishes the epithelium and absorbs nutrients
Contains lymph nodes (part of MALT) important in defense against bacteria
- Mucosa: Epithelial Lining
Consists of simple columnar epithelium and mucus-secreting goblet cells
A. The mucus secretions:
1. Protect digestive organs from digesting themselves
2. Ease food along the tract
a. Stomach and small intestine mucosa contain:
1. Enzyme-secreting cells
2. Hormone-secreting cells (making them endocrine and digestive organs)
Mucosa
Lines the lumen of the alimentary canal
Its three major functions are:
a. Secretion of mucus
b. Absorption of the end products of digestion
c. Protection against infectious disease
Consists of three layers:
1. A lining epithelium
2. Lamina propria
3. Muscularis mucosae
Hepatic portal circulation
- Collects nutrient-rich venous blood from the digestive viscera
- Delivers this blood to the liver for metabolic processing and storage
Arteries and the organs they serve include
A. Celiac trunk- hepatic, splenic, and left gastric: spleen, liver, and stomach
B. Superior and Inferior mesenteric: small and large intestines
Peritoneal organs (intraperitoneal)
organs surrounded by peritoneum(ex liver)
Retroperitoneal organs
organs outside the peritoneum (ex kidneys)
Mesentery
double layer of peritoneum that provides:
a. Vascular and nerve supplies to the visceral organs
b. A means to hold digestive organs in place and store fat
Peritoneal fluid
- Lubricates digestive organs
- Allows them to slide across one another
Peritoneum
serous membrane of the abdominal cavity
Visceral Peritoneum
covers external surface of most digestive organs
Parietal Peritoneum
lines the body wall
Small Intestines
a. Peptidase- Peptides>amino acids
b. Sucrase- Sucrose>glucose
c. Maltase- Maltose>glucose
d. Lactase- Lactose>glucose
Pancreas
a. Amylase- Cabohydrates>glucose
b. Trypsin- Polypeptides>peptides
c. Lipase- Fats>fatty acids
Liver
a. Bile Salts
- breakdown of fats into fatty acids
Stomach
a. Pepsin
-breaks Proteins into polypeptides
b. HCl (Ph 1-2)
-breaks pepsinogen into pepsin
-destroys pathogens
