Digestion, Absorption, and Metabolism

Flashcards covering digestive system anatomy, tissue layers, enzymatic functions, nutrient transport pathways, digestive health conditions, and cellular respiration based on lecture notes.

What are the four primary types of tissues that make up organs in the human body?

Muscle, nerve, epithelial, and connective tissue.

What are the four structural tissue layers that make up the wall of the gastrointestinal (GI) tract from the inside out?

1. Mucosa (innermost protective lining that absorbs nutrients), 2. Connective tissue layer (contains nerves and blood vessels), 3. Layers of smooth muscle (mixes and propels food), 4. External layer of connective tissue (provides support and protection).

What is the typical transit time for food to pass from ingestion to elimination as solid waste in a healthy adult?

Between $24$ and $72\,\text{hours}$.

How do phagocytes and lymphocytes collaborate to protect the body against pathogens in the gastrointestinal tract?

Phagocytes target, engulf, and break up invading organisms to present their antigens on the surface. Lymphocytes recognize these presented antigens and produce specific antibodies that bind to and destroy them.

What two enzymes are present in saliva, and what are their specific functions in the mouth?

Salivary amylase breaks starch down into smaller carbohydrate molecules, and lysozyme inhibits the growth of bacteria that cause tooth decay.

What function does the epiglottis perform during the swallowing process?

The epiglottis blocks the air passage to the lungs, ensuring that the bolus of food passes safely down the esophagus toward the stomach.

What roles do parietal cells and chief cells play in stomach gastric glands?

Parietal cells produce hydrochloric acid to acidify stomach contents and kill bacteria; chief cells produce pepsinogen, an inactive precursor activated into pepsin to digest proteins.

How does meal composition influence the rate of gastric emptying?

High-fat meals remain in the stomach longest because hormones slow GI motility; protein-rich meals leave faster; carbohydrate-rich meals leave the fastest.

What are the three sections of the small intestine in order, along with their respective lengths?

Duodenum ($30\,\text{cm}$), jejunum ($2.4\,\text{m}$), and ileum ($3.3\,\text{m}$).

How do secretin and cholecystokinin (CCK) coordinate digestive secretions in the small intestine?

Secretin prompts the release of bicarbonate-rich pancreatic juice and stimulates bile production in the liver; CCK triggers enzyme-rich pancreatic juice release and causes the gallbladder to contract and release bile.

According to Table 3.2 on enzyme functions, which specific digestive enzymes in the small intestine break down disaccharides?

Sucrase (breaks sucrose into glucose and fructose), lactase (breaks lactose into glucose and galactose), and maltase (breaks maltose into glucose).

How do facilitated diffusion and active transport differ regarding energy and concentration gradients across the mucosal layer?

Facilitated diffusion moves substances down a concentration gradient using a carrier molecule without requiring energy; active transport uses a carrier molecule and consumes cellular energy (ATP) to transport substances against a concentration gradient.

What is dysbiosis, and what health conditions are linked to it?

Dysbiosis is an imbalance in intestinal microflora leading to inflammation and impaired immune function. It is associated with IBS, celiac disease, inflammatory bowel disease, obesity, cardiovascular disease, diabetes, allergy, asthma, and neurological illnesses.

What is the difference between enteral tube-feeding and total parenteral nutrition (TPN)?

Enteral feeding provides a liquid diet directly to the stomach or intestine through a tube; total parenteral nutrition (TPN) delivers all required nutrients directly into the circulatory system via intravenous access.

Why is the enzyme rennin present in an infant's stomach, and what does it do?

Rennin is produced in the infant stomach to cause the milk protein casein to curdle, aiding in milk protein digestion.

What is atrophic gastritis, and why is it significant in elderly populations?

Atrophic gastritis is inflammation of the stomach lining that reduces stomach acid production, leading to bacterial overgrowth in elderly individuals.

Which vascular routes transport water-soluble vs. fat-soluble nutrients away from the digestive tract?

Water-soluble nutrients enter capillaries of the hepatic portal circulation directly to the liver; non-water-soluble fat products enter lacteals of the lymphatic system before draining into the systemic bloodstream.

What are the three main mitochondrial steps involved in producing ATP through cellular respiration?

1. Glucose, fatty acids, and amino acids are converted into acetyl-CoA ($\text{C-C-CoA}$). 2. Acetyl-CoA is broken down in the citric acid cycle to release carbon dioxide ($\text{CO}_2$) and high-energy electrons. 3. Electrons are shuttled to the electron transport chain to generate ATP and form water ($\text{H}_2\text{O}$).

According to the Digestive Problems table, what are the primary causes, consequences, and medical treatments for stomach ulcers?

Causes: H. pylori bacterial infection, chronic use of NSAIDs like aspirin or ibuprofen, or GERD. Consequences: Pain, bleeding, and potential abdominal infection. Treatment: Antibiotics to treat infection, antacids to reduce acid, and medication adjustment.

According to the Bristol Stool Chart, which stool types classify constipation and diarrhea?

Type 1 (separate hard lumps) indicates severe constipation; Type 6 (fluffy pieces with ragged edges) and Type 7 (entirely liquid stool) indicate diarrhea.