Digestive System

What is the function of the lips in the oral cavity?

They serve as a transition between skin and mucous membrane, appearing pinkish due to a thin epidermis.

What is the role of the tongue in digestion?

The tongue is a skeletal muscle that helps form a bolus of food and is important for speech.

What is the lingual frenulum?

A fold of mucous membrane under the tongue that holds it in place.

What are the two types of palates in the oral cavity?

The hard palate, made of mucous membrane and bones, and the soft palate, made of skeletal muscle and mucous membrane.

What is ankyloglossia?

A condition where the lingual frenulum is too short and restricts the tongue's range of motion, potentially causing difficulties with speech and breastfeeding.

What are the three types of salivary glands?

Parotid glands, submandibular glands, and sublingual glands.

What is the primary composition of saliva?

Saliva is mostly water (99%), with some mucous, antimicrobial chemicals, antibodies, and enzymes like amylase.

How are salivary glands controlled?

They are innervated by the sympathetic and parasympathetic nervous systems, with sympathetic activity inhibiting salivation and parasympathetic activity stimulating it.

What is mumps?

A viral infection that affects one or more salivary glands, usually the parotid, causing pain, swelling, and fever.

What is Sjögren Syndrome?

An autoimmune disorder that destroys salivary and tear glands, leading to dry mouth (xerostomia) and dry eyes (xerophthalmia).

What are the three regions of the pharynx?

The nasopharynx, oropharynx, and laryngopharynx.

What is the function of the pharyngeal constrictor muscles?

They contract sequentially to move food through the pharynx and into the esophagus.

What is the esophagus?

A tube that travels from the pharynx to the stomach, containing upper and lower esophageal sphincters.

What is gastroesophageal reflux?

A condition where acidic stomach contents enter the esophagus, often due to a weak lower esophageal sphincter.

What is a hiatal hernia?

A condition where part of the stomach extends through the esophageal hiatus into the thoracic cavity, increasing acid reflux.

What are the four basic tissue layers of the stomach?

Mucosa, submucosa, muscularis, and serosa.

What is pyloric stenosis?

A condition characterized by thickening of the pyloric sphincter, narrowing the opening into the duodenum and causing projectile vomiting in infants.

What are the risk factors for pyloric stenosis?

Being male, having a family history, being a pre-term baby, and maternal smoking.

What is the role of the pylorus in the stomach?

It regulates the movement of materials from the stomach to the duodenum.

What is the function of the gastroesophageal sphincter?

To prevent the backflow of stomach contents into the esophagus.

What happens during swallowing?

Food is mixed with saliva to form a bolus, which is moved to the back of the mouth, and the soft palate elevates to close off the nasopharynx.

What is the significance of the esophageal hiatus?

It is the hole in the diaphragm through which the esophagus passes to connect with the stomach.

What are the symptoms of mumps?

Pain, swelling, tenderness of the salivary glands, fever, and headache.

What is the treatment for ankyloglossia?

Non-surgical clipping of the frenulum to improve tongue mobility.

What is the primary enzyme found in saliva and its function?

Amylase, which begins the digestion of starches (carbohydrates).

What are the three layers of muscle in the stomach's muscularis?

The stomach has a layer of longitudinal muscle, a layer of circular smooth muscle, and an inner layer of oblique smooth muscle.

What is the function of the oblique smooth muscle layer in the stomach?

It allows for mechanical digestion through mixing, pummeling, and churning of food.

What is chyme?

Chyme is a creamy, pasty substance formed by mixing food with gastric juice.

What is the gastric mucosa?

The gastric mucosa is the inner lining of the stomach that lies in longitudinal folds called rugae.

What are gastric pits?

Gastric pits are microscopic infolds of the gastric mucosa that lead to gastric glands.

What do gastric glands secrete?

Gastric glands secrete gastric juice, approximately 2 to 3 liters per day.

What is the role of chief cells in the stomach?

Chief cells secrete pepsinogen, which is activated to pepsin in the acidic environment of the stomach.

What is the function of hydrochloric acid (HCl) in the stomach?

HCl activates pepsinogen to pepsin, begins protein digestion, inactivates amylase, kills most microbes, and denatures proteins.

What is intrinsic factor and its importance?

Intrinsic factor is secreted by parietal cells and is necessary for the absorption of Vitamin B12.

What do mucous cells secrete and why?

Mucous cells secrete thick alkaline mucous to protect the stomach mucosa from HCl.

What hormones do enteroendocrine cells secrete?

Enteroendocrine cells secrete hormones such as gastrin, serotonin, and histamine.

What is the effect of gastrin on gastric activity?

Gastrin increases the secretion of pepsinogen and HCl, enhancing gastric motility.

How does serotonin affect the stomach?

Serotonin increases the contraction of the gastric muscularis, enhancing mechanical digestion.

What is the role of histamine in the stomach?

Histamine increases the secretion of HCl but does not cause inflammation in the stomach.

What are the phases of gastric activity control?

The phases are the cephalic phase, gastric phase, and intestinal phase.

What occurs during the cephalic phase of gastric activity?

The cephalic phase prepares the stomach for food through stimulation from sight, smell, taste, and the act of eating.

What triggers the gastric phase of gastric activity?

The gastric phase is triggered by the presence of food in the stomach, causing stretching and increased gastric motility and secretion.

What happens during the intestinal phase of gastric activity?

The intestinal phase primarily inhibits gastric activity to limit acidic stomach contents entering the duodenum.

What hormones are secreted during the intestinal phase to inhibit gastric activity?

Secretin and cholecystokinin (CCK) are secreted to inhibit gastric motility and secretions.

What is the enterogastric reflex?

The enterogastric reflex decreases gastric activity and tightens the pyloric sphincter to limit chyme passage into the duodenum.

What substances are minimally absorbed in the stomach?

Very little is absorbed in the stomach; some water, alcohol, and a few medications like aspirin can be absorbed.

What is the primary digestive enzyme secreted in the stomach?

Pepsin is the only digestive enzyme secreted in the stomach, beginning protein digestion.

What effect does HCl have on amylase?

HCl inactivates amylase, stopping starch digestion.

What is the function of rennin in infants?

Rennin curdles milk to slow digestion in infants.

What is the rate of mixing and churning waves in the stomach?

Mixing and churning waves occur at a rate of approximately three waves per minute.

What is the role of peristaltic waves in the stomach?

Peristaltic waves push small amounts of chyme through the pyloric sphincter into the small intestine.

Where is the pancreas located?

Posterior to the stomach.

What are the two types of glands the pancreas functions as?

Both an endocrine and exocrine gland.

What hormones do the pancreatic islets secrete?

Glucagon (from alpha cells) increases blood sugar, and insulin (from beta cells) decreases blood sugar.

What do acini cells secrete?

Pancreatic juice, which contains digestive enzymes.

What forms the hepatopancreatic ampulla?

The pancreatic duct joins with the common bile duct.

What is the composition of pancreatic juice?

Alkaline, neutralizes acidic stomach contents, and contains digestive enzymes.

What are the main digestive enzymes found in pancreatic juice?

Pancreatic amylase, pancreatic lipase, pancreatic nucleases, trypsin, chymotrypsin, and carboxypeptidase.

What hormones control pancreatic secretion?

Secretin, CCK (cholecystokinin), and GIP (gastric inhibitory peptide).

Where is the liver located?

Under the diaphragm in the right upper quadrant (RUQ).

How many lobes does the liver have?

Four lobes: right lobe, left lobe, caudate lobe, and quadrate lobe.

What are the two sources of blood supply to the liver?

Hepatic artery (oxygenated blood) and hepatic portal vein (deoxygenated blood from digestive organs).

What is a portal triad in liver lobules?

A structure consisting of a branch of the hepatic artery, hepatic portal vein, and hepatic (bile) duct.

What is the function of sinusoids in the liver?

They are wide, permeable capillaries that mix blood from the hepatic artery and hepatic portal vein.

What is the primary function of bile?

To emulsify fats and aid in their digestion.

What is the daily production of bile?

600-1000 mL per day.

What happens to bile when there is no food in the small intestine?

The sphincter at the end of the common bile duct closes, causing bile to back up into the cystic duct and gallbladder for storage.

What are the main components of bile?

Bile salts, bilirubin, cholesterol, salts, ions, and water.

What are some functions of the liver?

Detoxification, phagocytosis, protein synthesis, nutrient storage, carbohydrate metabolism, and fat metabolism.

What is hepatitis?

Inflammation of the liver, usually due to viral infection or alcoholism.

What is cirrhosis?

A condition where hepatocytes die and are replaced with scar tissue.

What is portal hypertension?

Increased blood pressure in the portal venous system, often leading to complications like varices.

What is the role of hepatocytes in liver function?

They clean blood in sinusoids and add or remove nutrients before blood enters the central vein.

What is the role of the gallbladder?

To store bile; it does not produce bile.

What is the primary function of the gallbladder?

To store and concentrate bile, removing water to make it 10X more concentrated than bile from the liver.

What is the typical storage capacity of the gallbladder?

40-60 mL.

What hormone stimulates the gallbladder to contract?

Cholecystokinin (CCK) from the duodenum.

What are gallstones primarily composed of?

Excess cholesterol crystals or build-up of bilirubin.

What is a common treatment for gallstones?

Cholecystectomy, which is the removal of the gallbladder or stones.

What are the three regions of the small intestine?

Duodenum, jejunum, and ileum.

How long is the small intestine?

Approximately 21 feet long.

What is the primary function of the duodenum?

To receive pancreatic juice and bile, and to join with the stomach at the pyloric sphincter.

Where does most absorption and digestion occur in the small intestine?

In the jejunum.

What initiates the opening of the ileocecal sphincter?

The gastroileal reflex and gastrin from the stomach.

What are the three modifications of the small intestine that increase surface area?

Circular folds, villi, and microvilli.

What is the function of villi in the small intestine?

To increase surface area for absorption and contain lymphatic and blood capillaries.

What are brush border enzymes?

Digestive enzymes attached to microvilli that complete the digestion of nutrients.

What types of nutrients are absorbed in the small intestine?

Carbohydrates, proteins, nucleic acids, fats, water, and ions.

How are carbohydrates absorbed in the small intestine?

They are broken down into simple sugars (monosaccharides).

What happens to proteins during digestion in the small intestine?

They are broken down into amino acids.

How are fats absorbed in the small intestine?

Fats are absorbed into the lacteal (lymphatic capillary) and enter the blood at the thoracic duct.

What is malabsorption syndrome?

A condition where the small intestine fails to properly absorb nutrients, leading to symptoms like bloating and anemia.

What are the main functions of the large intestine?

To complete absorption of water, ions, and vitamins, and to excrete waste.

What anatomical features distinguish the large intestine?

Longitudinal muscle in three strips (teniae coli), haustra (pouches), and epiploic appendages (fat blobs).

What is the function of the appendix?

Its function is not well understood, but it may play a role in gut flora maintenance and immunity.

What is appendicitis?

Inflammation of the mucus lining of the appendix, which is a medical emergency requiring removal.

What is the length and diameter of the large intestine?

5 feet long and 2 inches in diameter.

What are the two main types of digestion that occur in the large intestine?

Mechanical digestion and chemical digestion.

What is haustral churning?

A mechanical digestion process that moves material from one haustra (pouch) to the next.

What triggers mass peristalsis in the large intestine?

The gastrocolic reflex triggered by food in the stomach.