Digestive system A&P Test 2

What are the primary functions of the digestive system?

The digestive system carries out mechanical and chemical digestion, ingestion, propulsion, absorption, and defecation.

What is the difference between mechanical and chemical digestion?

Mechanical digestion breaks down large food pieces into smaller ones without altering their chemical composition. Chemical digestion uses enzymes to convert food particles into simpler chemicals.

What are the two main portions of the digestive system?

The alimentary canal and the accessory organs.

What are the accessory organs of the digestive system, and what role do they play?

The salivary glands, liver, gallbladder, and pancreas; they secrete substances that aid digestion but do not directly transport food.

How does the alimentary canal function as a food passageway?

It is a muscular tube about 8 meters long that extends from the mouth to the anus, moving food through various organs involved in digestion.

What are the four layers of the alimentary canal wall, and what are their functions?

Mucosa: Secretes mucus and enzymes, absorbs nutrients. Submucosa: Supports tissues, transports absorbed molecules. Muscularis: Moves the tube and food via peristalsis. Serosa: Reduces friction with serous fluid.

How does the mucosa layer aid in digestion?

It secretes mucus and enzymes while absorbing nutrients from food.

What is the role of the submucosa in nutrient absorption?

It contains blood vessels that transport absorbed food molecules.

How do the muscularis and serosa layers contribute to the movement of food?

The muscularis propels food through the canal using peristalsis, while the serosa provides lubrication to reduce friction.

What are the two types of movements in the alimentary canal, and how do they function?

Mixing movements: Mix food without moving it forward. Propelling movements (peristalsis): Move food through the canal.

What are the functions of the mouth in digestion?

Ingests food, breaks it down mechanically, mixes it with saliva, and begins chemical digestion of carbohydrates.

How do the lips and cheeks assist in the digestive process?

Lips sense texture and temperature; cheeks help hold food and assist in chewing.

What are the different parts of the tongue, and what roles do they play?

The tongue has taste buds (papillae), the lingual frenulum (attaches it to the mouth floor), and lingual tonsils (immune function).

How do the hard and soft palates contribute to digestion?

The hard palate provides structure, and the soft palate (with the uvula) prevents food from entering the nasal cavity.

What are the different types of teeth, and what are their functions?

Incisors (biting), Canines (tearing), Premolars & Molars (grinding).

How do teeth contribute to mechanical digestion?

They break food into smaller pieces, increasing surface area for enzymes.

What are the three major salivary glands, and where are they located?

Parotid glands (near ears), Submandibular glands (under the jaw), Sublingual glands (under the tongue).

How do serous and mucous cells contribute to saliva production?

Serous cells produce watery fluid with amylase, while mucous cells secrete mucus.

What is the function of salivary amylase in digestion?

It begins carbohydrate digestion by breaking starch into disaccharides.

How does saliva help in food processing before swallowing?

It moistens food, forms a bolus, and contains enzymes for digestion.

What are the three parts of the pharynx, and what are their roles?

Nasopharynx (air passage), Oropharynx (food & air passage), Laryngopharynx (connects to the esophagus).

How does the esophagus transport food to the stomach?

Through peristalsis, a wave-like muscle contraction.

What are the three stages of the swallowing mechanism?

Voluntary (bolus formed), Reflex (swallowing triggered), Peristaltic transport (food moves to stomach).

How does the lower esophageal sphincter prevent acid reflux?

It closes to prevent stomach contents from entering the esophagus.

What are the four main regions of the stomach?

Cardia, Fundus, Body, Pylorus.

How do the layers of the stomach wall aid in digestion?

Muscular layers churn food and gastric juices for digestion.

What are the components of gastric juice, and what are their functions?

Pepsin (protein digestion), HCl (activates pepsin), Mucus (protects lining), Intrinsic factor (B12 absorption).

How is gastric secretion regulated by neural and hormonal mechanisms?

Neural: Parasympathetic increases secretion, sympathetic decreases. Hormonal: Gastrin increases secretion, somatostatin inhibits acid.

What substances are absorbed in the stomach?

Water, alcohol, salts, and lipid-soluble drugs.

How does the pancreas function as both an endocrine and exocrine gland?

It secretes insulin and glucagon (endocrine) and digestive enzymes (exocrine).

What are the components of pancreatic juice, and what do they digest?

Amylase (carbs), Lipase (fats), Proteases (proteins), Nucleases (DNA/RNA).

How is the release of pancreatic juice regulated?

By hormones Secretin (bicarbonate release) and CCK (enzyme release).

What is the role of bicarbonate ions in digestion?

Neutralize stomach acid in the small intestine.

What are the primary functions of the liver?

Detoxification, metabolism, bile production, blood filtering, and storage.

How does the liver contribute to metabolism?

It processes glucose, proteins, and lipids and stores nutrients.

What are bile salts, and how do they aid in digestion?

They emulsify fats, increasing surface area for lipase.

How does the gallbladder store and release bile?

Stores bile and releases it into the duodenum via the common bile duct.

What are gallstones, and how do they form?

Crystals of cholesterol and bile salts that can block bile flow.

What are the three main parts of the small intestine?

Duodenum (shortest, receives bile and pancreatic juices), Jejunum (middle, main absorption site), Ileum (longest, absorbs remaining nutrients).

How do villi and microvilli increase absorption efficiency?

They increase surface area, allowing for more nutrient absorption.

How does aging affect digestion and nutrient absorption?

Slower peristalsis, reduced enzyme secretion, decreased absorption of nutrients.

What are some common digestive system issues in elderly individuals?

Heartburn, constipation, nutrient deficiencies, and lactose intolerance.

What is mucus?

• Secreted by goblet cells

• Also secreted by specialized Brunner’s glands, that secrete a thick,

alkaline mucus in response to certain stimuli

• Mucus secretion occurs in response to mechanical

stimulation, or presence of irritants such as gastric juice

• Contact with chyme stimulates goblet cells to secrete

mucus, and intestinal glands to secrete watery fluid

What is watery fluid in small intestine?

Secreted by intestinal glands

• Picks up digestion products, and transports them into villi

• Does not contain digestive enzymes

Enzymes in small intestine microvilli

• Peptidases: Break down peptides into amino acids

• Sucrase, maltase, lactase: Break down disaccharides into

monosaccharides

• Lipase: Breaks down fats into fatty acids and glycerol

How does peristalsis change with age?

It slows down, leading to issues like constipation and acid reflux.

What are the effects of aging on teeth and gum health?

Enamel thins, gums recede, teeth may loosen or fall out, increasing risk of oral health issues.

What are the main functions of the large intestine?

Absorption of water and electrolytes, formation and storage of feces, and housing beneficial bacteria.

How does the structure of the large intestine differ from the small intestine?

The large intestine lacks villi, has a wider diameter, and features taeniae coli (bands of smooth muscle) that form haustra (pouches).

What are the parts of large intestine?

Cecum:

• Pouch, forms beginning of large intestine

• Appendix is attached to cecum; lymph nodules in appendix function in the

immune response

Colon:

• Ascending, transverse, descending and sigmoid portions

• Contains hepatic (right colic) and splenic (left colic) flexures

Rectum:

• Extends from sigmoid colon to anal canal

• Lies next to sacrum

Anal canal:

• Last 2.5 to 4 cm of large intestine; opens to outside as anus

• Internal and external anal sphincters guard anus

What role do intestinal bacteria play in digestion?

They break down cellulose, synthesize vitamins (K, B12, thiamine), and produce gas.

What are the steps in the defecation reflex?

Feces enter the rectum, stretch receptors trigger peristaltic waves, the internal anal sphincter relaxes, followed by voluntary relaxation of the external sphincter.

What causes conditions like diverticulosis and inflammatory bowel disease?

Diverticulosis: Weakening of intestinal walls causing pouches. IBD (Ulcerative colitis & Crohn’s disease): Chronic inflammation of intestines.

How does colorectal cancer develop, and what are common screening methods?

It results from uncontrolled cell growth in the colon/rectum. Screening tests include fecal occult blood tests and colonoscopies.

How is carbohydrate digestion and absorption carried out in the small intestine?

Salivary and pancreatic amylase break starch into disaccharides, which are then broken down into monosaccharides and absorbed into the bloodstream.

What is the role of bile salts in fat digestion?

They emulsify fats into small droplets, increasing surface area for lipase.

What are micelles and chylomicrons, and how do they aid in fat absorption?

Micelles transport fatty acids to the microvilli for absorption. Chylomicrons package triglycerides and transport them into the lymphatic system.