Chapter 24 Digestive System Study Prompts

What is the function of the gastrointestinal tract? What is the other name for this structure?

• Breakdown food, absorb nutrient molecules and eliminate indigestible foodstuffs.

• Alimentary canal.

The alimentary canal is composed of which structures?

mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus

Can you list the accessory digestive organs?

teeth, tongue, salivary glands, liver, gall bladder, pancreas

Can you list and describe the various digestive activities?

Activities:

1. Ingestion- taking food into the mouth

2. Mechanical digestion- physical breakdown of the food- chewing, churning, segmentation

3. Chemical digestion- breakdown of food using chemicals like enzymes and acid

4. Propulsion- movement of food- swallowing and peristalsis

5. Absorption- bringing food across the mucosa and into the blood supply

6. Elimination- passing feces out of the body

What is the difference between peristalsis and segmentation?

• peristalsis is smooth muscle wave-like contractions that move food in one direction along the GI tract (propulsion).

• Segmentation is smooth muscle back-and-fourth contractions to mix and further break down food physically (mechanical digestion).

Can you describe the peritoneum structures?

• The peritoneum is made of a serous, two-layer membrane.

• One layer lines the cavity walls in the abdomen (parietal peritoneum) and the other lines some of the organs of the abdominal cavity (visceral peritoneum).

Can you describe the peritoneal cavity? What is the function of the fluid in this cavity?

• the space between the parietal and visceral peritoneal membranes.

• The serous fluid in this space acts as a lubricant to reduce the friction caused by the movements of the organs within the cavity.

Do you know the difference between retroperitoneal and intraperitoneal organs?

• retroperitoneal organs are not a part of the peritoneal linings, and therefore are "behind" the membranes (liver, kidneys, duodenum).

• The organs lined by these membranes are
  "within" the membrane layers and are therefore intraperitoneal (small and large intestines).

Can you describe the structure and function of mesenteries?

mesentaries are double serous membranes in the abdomen that tether organs to the posterior body wall.

Can you list the four layers of the alimentary canal from the lumen outwards?

1. What is the predominant tissue type of each tunic?

2. What is the major function of each tunic?

Layers:

1. Mucosa- epithelia (stratified squamous or simple columnar). This tissue will protect, or do secretion or absorption, depending on the location of the canal.

2. Submucosa- CT. contains the blood supply and nervous structures. Also has lymphatic structures for immune function.

3. Muscularis- skeletal or smooth muscle depending on the part of the tube, but will perform swallowing, peristalsis or segmentations

4. Serosa/adventitia- most superficial layer. Depending on the part of the canal, it will either be serosa (visceral peritoneum; small intestine) or CT, which is called fibrous adventitia (esophagus).

Can you describe the enteric nervous system of the alimentary canal?

• Local nervous structures of the gut.

• They communicate with the parasympathetic control by the brain as well.

What are the anatomical names for the mouth?

• What are the boundaries for this cavity?

1. oral or buccal cavity

   1. lips, palate, tongue and cheeks

What is the epithelia type that lines the oral cavity? How does this help withstand abrasion?

stratified squamous: many protective layers and the layers can slough and be replaced

Can you describe the structure and function of the lips and cheeks? Do you know the anatomical name for the lips?

1. What type of muscle is found in the lips and cheeks?

2. What is the name of the muscles that control the lips and cheeks?

1. Speech, chewing and facial expression. They are called labia.

   1. the lips and cheeks have skeletal muscle cores. They help in chewing and speech.

   2. The names of the skeletal muscles are the buccinators in the cheeks and orbicularis oris in the lips.

Can you describe the location, structure and function of the following?

1. Hard palate

2. Soft palate

C. Fauces

Terms:

a. Hard palate- bony portion of the palate. Chewing and speech

b. Soft palate- skeletal muscle core. Soft part of palate. Contains uvula, which closes off the nasopharynx during swallowing. Used in swallowing.

c. Fauces- archway to the oropharynx from the oral cavity

Can you describe the location and function of the tongue?

• floor of the mouth.

• Chewing (forms bolus) and speech, and swallowing

What type of muscle is the tongue made of?

skeletal

Can you list and describe the three types of papillae on the tongue? Which of them have taste buds?

Types:

1. Fungiform- numerous, small and contains taste buds. Mostly on the tongue, but also found in other places in the oral cavity

2. Circumvallate- large, have taste buds and form a "y" formation on the back 2/3 of tongue.

3. Filiform- on tongue. Small and provide friction. NO TASTE BUDS

What are the functions of salivary glands?

secrete saliva to cleanse the mouth and help form the bolus

Can you list and give the location for the three sets of salivary glands?

Gland:

1. Parotid- anterior to the ear. Duct opens to the upper 2nd molar region.

2. Submandibular- under the mandible and duct opens to the lingual frenulum

3. Sublingual- under the tongue and duct opens to the floor of the mouth. 10-12 ducts.

Can you describe the composition of saliva? How much is produced each day?

• Mostly water.

• Also contains mucus, ions, and immune molecules (antibody, defensins and lysozyme).

• The enzyme amylase breaks down starches into simple sugars.

• 1-1.5L per day (you won't be tested on the amount).

Can you list and describe the function of the different types of teeth?

Types:

1. Incisor- nipping and cutting

2. Eyetooth/canine- piercing and cutting

3. Premolars and molars- grinding and crushing

Can you describe the following tooth structures? Can you diagram them?

1. Root

2. crown

3. neck

4. dentin

5. enamel

6. cementum

7. peridontal ligament

8. gingiva

See lecture ink for structure drawings. Descriptions:

1. Root- portion embedded in maxilla/mandible

2. Crown- visible portion of tooth

3. Neck- constricted portion between root and crown

4. Dentin- bone-like material that makes up the bulk of the tooth

5. Enamel- hydroxyapatite crystals arranged on the crown in the manner that makes it the hardest substance in the human body.

6. Cementum- calcified CT around the root of the tooth that helps "cement" the tooth in the socket

7. Periodontal ligament- ligaments that anchor tooth in socket

8. Gingiva- gums

Can you list the parts of the pharynx?

nasopharynx, oropharynx and laryngopharynx

Can you describe the structure and function of the oropharynx? What kind of epithelia lines it?

• receives foodstuff from the oral cavity and leads it to the laryngopharynx.

• Stratified squamous epithelia.

Can you describe the structure and location of the esophagus?

• tube of the alimentary canal that stretches from the laryngopharynx to the stomach.

• Runs through the mediastinum.

What is the region of the stomach called where the esophagus joins?

cardia

What is the name of the sphincter that controls the entrance to the stomach from the esophagus?

cardiac sphincter/ gastroesophageal sphincter

What are the characteristics of the esophagus?

soft, collapsed tube about 10 inches in length

Can you list the digestive processes that occur from the mouth to the stomach?

ingestion, chemical digestion, mechanical digestion, swallowing (deglutition), peristalsis

What is food called when it leaves the mouth and travels to the stomach?

bolus

What are the processes of the stomach? What is the food called when it leaves the stomach?

• churning (mechanical digestion), chemical digestion and storage.

• Chyme.

Can you describe the following stomach structures? Can you diagram them?

1. Fundus

2. Body

3. Pyloric region

4. Pyloric sphincter

5. Greater and lesser curvatures

6. Greater and lesser omentum

See diagram in lecture ink. Descriptions:

1. Fundus- domed, superior region of the stomach

2. Body between the fundus/cardia and the pyloric region. Bulk of the stomach

3. Pyloric region- end of the stomach before the pyloric sphincter

4. Greater curvature- lateral edge; lesser curvature- medial edge

5. Greater omentum- large double serosa membrane attached to the greater curvature; lesser omentum- double serosa connecting the liver to the stomach

Can you describe the muscularis layer of the stomach?

3 layers- deepest is the oblique (not present in the rest of the canal), then circular, then superficial longitudinal layer.

Can you describe the epithelia lining of the stomach?

simple columnar epithelia.

Can you describe the structure and function of gastric pits and gastric glands?

• What chemicals are secreted from them?

• gastric pits are made of mucus cells that make and secrete mucus to provide a protective lining to protect the stomach from its own acid.

• The gastric glands include parietal cells that secrete HCl and Chief cells that secrete pepsinogen, which is then cleaved to pepsin, which digests proteins

What is the function of rugae in the stomach?

Allows the stomach to expand and store food.

Do you know how the stomach keeps from digesting itself?

the mucus cells of the gastric pits produce a bicarbonate-rich mucous that lines the stomach mucosa and neutralizes acid

Can you describe digestive activities in the stomach?

churning (mechanical digestion) and chemical digestion (acid and pepsin)

What is the starting and ending structure of the small intestine?

starts at the pyloric valve and ends at the ileocecal valve.

What are the three subdivisions of the small intestine?

duodenum, jejunum and ileum

What accessory structures secrete into the duodenum?

Pancreas- pancreatic juices; Liver- bile

How is the small intestine anchored in the abdomen?

by mesentaries

Can you list and describe the structural modifications that increase surface area in the small intestine?

macroscopic folds similar to rugae, microscopic villi (finger-like projections) and microvilli (folded plasma membrane of the simple columnar apical surfaces)

Can you describe the epithelial lining of the small intestine?

• Brunner's glands? Crypts of Lieberkuhn?

• simple columnar in finger-like folds called villi.

• The bottoms of these folds are the Crypts of Leiberkuhn, which contain the enteroendocrine cells that secrete hormones.

• Brunner's glands are found in the duodenum and secrete bicarbonate to help neutralize the acidic chyme coming from the stomach.

What are the digestive activities of the small intestine?

segmentation (mechanical digestion), chemical digestion and absorption of nutrient molecules

Can you describe the structure of the liver? Where is the liver located?

• four lobes (right, left, caudate and quadrate).

• Located in the upper right quadrant of the abdomen.

What structure suspends the liver from the diaphragm and the abdominal wall?

falciform ligament

Can you list the activities of the liver?

makes bile, metabolizes nutrients from the intestines, detoxifies blood, immunity, makes plasma proteins, stores glycogen, recycles hemoglobin and produces urea

What anchors the liver to the stomach?

lesser omentum

What is the liver's association with the gall bladder?

the liver makes the bile that will be led to and stored in the gall bladder until a meal is eaten.

Can you give the name of the cells that make bile? What are the pathways in the liver called that the bile is secreted into?

• hepatocytes make the bile.

• It then enters the bile canaliculi and then travels out of the liver to the gall bladder, which will then ultimately enter the duodenum

Can you describe the microscopic anatomy of the liver?

• organized into lobules that are hexagonal plates of liver cells called hepatocytes.

• Each plate has a vein in the center called the central vein

Do you know the functions of hepatocytes?

• these cells perform all of the function of the liver- see #51

Do you know what liver sinusoids are?

leaky capillaries that flow through the liver lobules past the hepatocytes

What is the function of Kupffer cells?

immune cells that act as phagocytes in the liver to cleanse the blood flowing through it

Can you describe the structure and function of the gall bladder?

• stores and concentrates bile.

• A muscular walled sac that appears green found on the ventral surface of the liver.

What is the function of the gall bladder rugae?

same as stomach- allows gall bladder to expand outwards as it fills with bile

How does the gall bladder expel bile?

when we eat a meal the gall bladder will contract and expel the bile back into the cystic duct.

Can you describe the structure, location and function of the pancreas?

triangular shaped gland inferior and posterior to the stomach that has endocrine and exocrine functions.

What is the name of the duct that digestive juices are secreted from the pancreas?

main pancreatic duct

What is the name of the exocrine cells of the pancreas?

acinar/acini

What is pancreatic juice made of?

various enzymes such as amylase, trypsinogen, lipase, nucleases in aqueous solution

Do you know the starting and ending structure of the large intestine?

ileocecal valve to anus

Do you know the length of the large intestine?

approximately 1.5m

What is the main function of the large intestine?

absorb water

Can you list and describe the functions of the unique features of the large intestine?

structure:

1. tenia coli- longitudinal bands of smooth muscle that form huastra

2. huastra- pockets of the large intestine that aid in water absorption and movement in the large intestine

3. epiploic appendages- fat-filled pockets formed by the visceral peritoneum

Can you list, in order, the subdivisions of the large intestines?

cecum, ascending colon, right colic flexure, transverse colon, left colic flexure, descending colon, sigmoid colon, rectum, anal canal, anus

What is the vermiform appendix and where is it located?

• located on the cecum.

• Worm-like structure that serves no purpose in humans

Can you list, in order, the regions and flexures of the colon?

cecum, ascending colon, right colic flexure, transverse colon, left colic flexure, descending colon, sigmoid colon, rectum, anal canal, anus

Can you describe the muscle type of the internal and external anal sphincters? Which one is under voluntary control?

• internal anal sphincter is smooth muscle, involuntary and under control of the spinal cord.

• The external anal sphincter is skeletal muscle and voluntary

Do you know the location and function of mesocolon?

tethers the large intestine to the back of the body wall, primarily at the transverse and sigmoid regions

What is the epithelia type of the large intestine?

simple columnar until the anal canal and anus, which is stratified squamous epithelia

What are haustra, how are they formed and what are they for?

cecum, ascending colon, right colic flexure, transverse colon, left colic flexure, descending colon, sigmoid colon, rectum, anal canal, anus

How is defecation stimulated?

• stretch from the fecal matter in the rectum stimulates the spinal cord to relax the internal anal sphincter.

• We consciously control the external when it is appropriate to defecate

What is diarrhea? Constipation?

• hypermotility of the large intestine- not enough water is absorbed and runny stool results.

• Hypomotility- too much water is absorbed and the stool becomes hardened and difficult to pass.