Human Digestive System Quiz

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Questions and Answers

Which component of the stomach is primarily responsible for producing chyme?

Fundus

Body (correct)

Cardia

Pyloric antrum

What is the primary function of the gastric pits in the stomach?

To produce gastric mucus

To release gastric acid (correct)

To absorb nutrients

To secrete digestive enzymes (correct)

What role does the pyloric sphincter play in digestion?

Facilitates the absorption of nutrients

Controls the flow of chyme into the duodenum (correct)

Regulates gastric acid secretion

Prevents bile from entering the stomach

What is the primary consequence when the gastroesophageal sphincter does not function properly?

Reflux of gastric contents into the esophagus Signup and view all the answers

Which type of cells in the stomach are primarily responsible for secreting hydrochloric acid (HCl)?

Parietal cells Signup and view all the answers

What is the primary function of the alimentary canal?

To digest food Signup and view all the answers

Which accessory organ is NOT part of the digestive system?

Bladder Signup and view all the answers

During which digestive process does the esophagus facilitate movement of food?

Peristalsis Signup and view all the answers

What type of epithelium lines the esophagus?

Stratified squamous epithelium Signup and view all the answers

Which part of the pharynx is associated with the digestive tract?

Oropharynx Signup and view all the answers

What role do hormones play in the digestive process?

They affect digestive actions. Signup and view all the answers

Which structure prevents the backflow of stomach contents into the esophagus?

Gastroesophageal sphincter Signup and view all the answers

Which term refers to the movement of food through the GI tract after ingestion?

Propulsion Signup and view all the answers

What is the primary digestive function of the liver?

Manufacture of bile Signup and view all the answers

Which component is NOT part of the portal triad within the liver?

Central vein Signup and view all the answers

Which structure is responsible for storing bile?

Gallbladder Signup and view all the answers

What are bile salts primarily responsible for in digestion?

Emulsifying fats Signup and view all the answers

Which of the following conditions is NOT typically associated with liver dysfunction?

Appendicitis Signup and view all the answers

What initiates the cephalic phase of gastric secretions?

Thinking about and tasting food Signup and view all the answers

Which part of the small intestine is primarily responsible for nutrient absorption?

Jejunum Signup and view all the answers

What is the primary function of the large intestine?

Water absorption and waste elimination Signup and view all the answers

Which cells in the small intestine are responsible for secreting mucus?

Goblet cells Signup and view all the answers

What is the role of the ileocecal valve?

To prevent backflow from the colon to the small intestine Signup and view all the answers

Which phase of digestion is characterized by the secretion of gastric juices triggered by the presence of food in the stomach?

Gastric phase Signup and view all the answers

Which structure in the digestive system primarily helps in the emulsification of fats?

Liver Signup and view all the answers

What is the primary role of the liver in digestion?

All of the above Signup and view all the answers

Which type of teeth are primarily used for crushing and grinding food?

Molars Signup and view all the answers

What type of muscle contraction is responsible for mixing and moving food along the digestive tract?

Peristalsis Signup and view all the answers

What is the primary function of lipases in the digestive process?

Emulsifying fats for absorption Signup and view all the answers

What role do CCK and secretin play in digestion?

They regulate the release of digestive enzymes and bile. Signup and view all the answers

Which of the following is an enzyme that breaks down proteins in the small intestine?

Trypsin Signup and view all the answers

Which substance is primarily absorbed in the small intestine along with monosaccharides and amino acids?

Electrolytes Signup and view all the answers

What occurs during the emulsification process?

Bile salts help break down large fat globules into smaller droplets. Signup and view all the answers

What is the main function of brush border enzymes in the small intestine?

Facilitating the absorption of nutrients into the bloodstream Signup and view all the answers

What is the function of duct cells in the digestive system?

To transport bile and pancreatic enzymes to the small intestine Signup and view all the answers

What condition is associated with the inability to properly digest lactose?

Lactose intolerance Signup and view all the answers

Study Notes

Digestive System

The digestive system breaks down food, absorbs nutrients, and eliminates waste.
The alimentary canal is the primary organ responsible for digesting and absorbing nutrients, while accessory organs assist in the process.

Alimentary Canal

The alimentary canal is also known as the gastrointestinal tract, digestive tract, or gut.
It's divided into the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.

Accessory Organs

Teeth: used for mechanical breakdown (mastication).
Tongue: aids in taste, mastication, and swallowing.
Gallbladder: stores and concentrates bile.
Glands:
- Salivary glands produce saliva (containing salivary amylase to break down carbohydrates).
- Liver produces bile (aids in fat digestion).
- Pancreas produces digestive enzymes and hormones.

Digestive Processes

Ingestion: process of taking food into the mouth.
Mechanical breakdown: physical breakdown of food into smaller particles (e.g., chewing, churning in the stomach).
Propulsion: movement of food through the digestive tract.
- Swallowing (deglutition) moves food from the mouth to the esophagus.
- Peristalsis: wave-like muscle contractions moving food along the GI tract.
- Segmentation: rhythmic contractions of the small intestine, mixing and breaking down food further.
Digestion: chemical breakdown of food into smaller molecules.
- Mechanical and chemical stimuli are detected by receptors in the GI tract, triggering responses from smooth muscle and glands.
- Neurons mediate reflexes, and hormones influence digestive activity.
Absorption: movement of digested nutrients into the bloodstream.
Defecation: elimination of undigested waste from the body.

Peritoneum

The peritoneum is a serous membrane that lines the abdominal cavity.
Mesentery: a double layer of peritoneum that supports and holds abdominal organs in place.
- Omenta: specialized mesenteries that aid in fat storage and immune function.
  - Greater omentum: hangs from the stomach, covering the intestines like an apron.
  - Lesser omentum: connects the stomach to the liver.
- Transverse mesocolon: supports the transverse colon.
Retroperitoneal: organs behind the peritoneum (e.g., kidneys).
Peritoneal: organs within the peritoneal cavity (e.g., stomach, small intestine).

Major Organs of the Alimentary Canal

Mouth:
- Stratified squamous epithelium lining.
- Ingestion and mastication (chewing) occur here.
- Contains salivary amylase for carbohydrate digestion.
- Palate (hard and soft) and uvula for speech and swallowing.
- Vestibule is the space between the teeth and cheeks.
- Gingivae (gums) surround the teeth.
- Labial frenula (sing. Labial frenulum) connects the lips to the gums.
Pharynx:
- Connects the mouth and esophagus.
- Three regions: Nasopharynx (not involved in swallowing), Oropharynx, and Laryngopharynx.
Esophagus:
- Mucosa layer: Stratified squamous epithelium.
- Submucosa, muscularis externa, and adventitia layers.
- Lumen is usually closed.
- Gastroesophageal sphincter (lower esophageal sphincter, cardial sphincter) controls food entry into the stomach.
- Deglutition (swallowing) is a 5-step process:
  - Buccal phase: voluntary, moves food from the mouth to the pharynx.
  - Pharyngeal-esophageal phase: involuntary, food moves through the pharynx and esophagus.
  - Peristalsis: wave-like muscle contractions propel food through the esophagus.
  - Gastroesophageal sphincter: relaxes to allow food into the stomach.
  - Gastroesophageal sphincter dysfunction can cause acid reflux.
Stomach:
- Regions: Cardia, Fundus, Body, Pyloric parts (pylorus).
  - Pyloric antrum: connects to the pyloric canal.
  - Pyloric canal: connects to the pyloric sphincter.
  - Pyloric sphincter (valve) controls the flow of chyme into the small intestine.
- Greater and lesser curvature.
- Rugae (folds of mucosa) increase surface area.
- Muscularis externa has an additional oblique layer for churning.
- Produces chyme, a semi-fluid mixture of food and gastric juice.
- Histology:
  - Gastric pits: depressions in the mucosa lining.
  - Gastric glands: produce gastric juice.
  - Parietal cells: produce hydrochloric acid (HCl) and intrinsic factor (important for vitamin B12 absorption).
  - Chief cells: produce pepsinogen (inactive form of pepsin).
    - Pepsinogen is converted to pepsin (active form) by HCl.
    - Pepsin breaks down proteins.
  - Enteroendocrine cells: produce hormones like gastrin, histamine, and others.
- Gastric ulcer: can be caused by H.pylori bacteria.
- Mechanical processes: churning and mixing of food with gastric juice.
- Regulation of digestive activities:
  - Gastric secretions: regulated by neural and hormonal controls.
    - Cephalic phase: begins in the head, triggered by sight, smell, or taste of food.
    - Gastric phase: triggered by the presence of food in the stomach.
    - Intestinal phase: triggered by the presence of chyme in the small intestine.
  - Gastric motility and emptying:
    - Stretch: stomach distends with food.
    - Peristalsis: propels food through the stomach.
    - Duodenum: releases hormones to regulate gastric emptying.
    - Food type: fatty foods slow down emptying compared to carbohydrates.
Small intestine:
- Divided into three segments: Duodenum, Jejunum, and Ileum.
- Surface area is increased by circular folds, villi, and microvilli (brush border).
- Brush border enzymes: break down nutrients further.
- Histology:
  - Enterocytes: absorb nutrients.
  - Goblet cells: produce mucus for lubrication.
  - Enteroendocrine cells: produce hormones like cholecystokinin (CCK) and secretin.
  - Paneth cells: produce antimicrobial peptides.
  - Intestinal crypts: indentations in the mucosa where stem cells regenerate epithelial cells.
  - Lymphatic system:
    - MALT (mucosa-associated lymphoid tissue) and Peyer's patches: protect against pathogens.
    - Lacteals: lymphatic vessels that absorb fats.
- Digestive activities: most nutrient digestion and absorption occur here.
- Regulation: controlled by chyme entry, motility, and hormones.
Large intestine:
- Ileocecal valve: controls food entry from the small intestine.
- Cecum: pouch at the beginning of the large intestine.
- Appendix: small, worm-like appendage extending from the cecum.
- Colon: divided into four parts:
  - Ascending colon
  - Transverse colon (supported by the transverse mesocolon).
  - Descending colon
  - Sigmoid colon
- Rectum: final part of the large intestine.
- Anus: external opening of the digestive tract.
  - Internal anal sphincter: involuntary smooth muscle.
  - External anal sphincter: voluntary skeletal muscle.
- Histology:
  - Thick mucosa: allows for water absorption.
  - Large crypts with many goblet cells: produce mucus for lubrication.
  - Bacterial microbiota (microbiota): trillions of bacteria living in the large intestine.
    - Fermentation: break down undigested carbohydrates.
    - Vitamin synthesis: produce vitamin K and some B vitamins.
    - Protection: protect against pathogens.
    - Immune system: contribute to immune system balance.
- Processes of movement:
  - Segmentation: further mixes food with intestinal secretions.
  - Peristalsis: propels waste towards the rectum.
    - Mass movements: strong peristaltic waves that move food through the colon.
  - Defecation: elimination of waste from the body.
    - Three steps:
      - Rectal filling: triggers the urge to defecate.
      - Reflex defecation: involuntary response to rectal filling.
      - Voluntary control: controlled by the external anal sphincter.

Accessory Organs of the Digestive System

Accessory organs of the mouth:
- Tongue: taste buds for taste perception, aids in mastication and swallowing.
- Teeth:
  - Deciduous/milk/baby/primary teeth: first set of teeth.
  - Permanent teeth: replace deciduous teeth.
    - Incisors: front teeth for biting.
    - Canines/eyetooth/cuspids: pointed teeth for tearing.
    - Bicuspids/premolars: flat teeth for grinding.
    - Molars: flat teeth for grinding.
  - Enamel: hard outer layer of the tooth.
  - Dentin: hard tissue beneath enamel.
  - Pulp: soft tissue containing nerves and blood vessels.
  - Crown: visible part of the tooth.
  - Root: portion embedded in the jawbone.
  - Neck: connects the crown and root.
  - Gingiva: gums surrounding the teeth.
- Lips and cheeks: help hold food in the mouth during chewing.
- Salivary glands:
  - Parotid salivary gland: largest salivary gland, produces watery saliva.
  - Sublingual salivary gland: produces a thick, mucus-like saliva.
  - Submandibular salivary gland: produces a combination of watery and mucus-like saliva.
Liver and gallbladder:
- Liver: performs many functions, including bile production (aids in fat digestion).
  - Lobes of the liver: Right, Left, Caudate, Quadrate.
  - Falciform ligament: peritoneal fold dividing the liver, not a true ligament.
  - Bare area: portion of the liver not covered by peritoneum.
  - Liver lobules: functional units of the liver.
    - Portal triad: contains the bile duct, portal vein, and portal arteriole.
      - Bile duct: collects bile from the liver.
        
        Bile: manufactured by hepatocytes, travels through bile canaliculi to the bile duct.
        
        Bile pigments: e.g., bilirubin.
        
        Bile salts: aid in fat digestion, recycled via enterohepatic circulation.
        
        Phospholipids: components of bile.
      - Portal vein: carries blood from the digestive system to the liver.
      - Portal arteriole: carries oxygenated blood to the liver.
    - Central vein: collects blood from the liver.
    - Liver sinusoids: spaces between liver cells where blood flows.
- Gallbladder: stores and concentrates bile produced by the liver.
  - Connects to the liver via the cystic duct.
Homeostatic imbalances of the liver & gallbladder:
- Hepatitis: inflammation of the liver.
  - Viral (e.g., hepatitis A, B, C).
  - Non-viral causes: alcohol, drugs, wild mushrooms.
  - Non-alcoholic fatty liver disease (NAFLD): caused by fat accumulation in the liver.
- Cirrhosis: chronic liver disease characterized by scarring.
- Gallstones: solid deposits in the gallbladder.
- Jaundice: yellowing of the skin and whites of the eyes, caused by bilirubin buildup.
- Pancreas:
  - Acini (sing. acinus): clusters of cells that produce digestive enzymes.
    - Acinar cells: produce enzymes (proteases, amylase, lipases, nucleases).
      - Enzymes are typically released in inactive forms and activated in the small intestine.
  - Duct cells: produce bicarbonate (neutralizes stomach acid).
Ducts of the accessory organs leading into the small intestine:
- Right and Left hepatic ducts: collect bile from the liver.
- Common hepatic duct: combines bile from the right and left hepatic ducts.
- Cystic duct: connects the gallbladder to the common hepatic duct.
- Bile duct: carries bile from the liver and gallbladder to the small intestine.
- Main pancreatic duct: carries pancreatic juice to the small intestine.
- Hepatopancreatic ampulla: point where the bile and pancreatic ducts join.
- Sphincter of Oddi: controls the flow of bile and pancreatic juice into the duodenum.
- Major duodenal papilla: opening into the duodenum where the bile and pancreatic ducts enter.
- CCK (cholecystokinin) and secretin: hormones that regulate the release of digestive enzymes, bile, and bicarbonate from the pancreas and gallbladder.

Physiology of digestion & absorption

Carbohydrates:
- Salivary amylase: begins carbohydrate digestion in the mouth.
- Pancreatic amylase: continues carbohydrate digestion in the small intestine.
- Brush border enzymes: complete carbohydrate digestion.
  - Dextrinase: breaks down dextrins.
  - Glucoamylase: breaks down starch.
  - Maltase: breaks down maltose.
  - Sucrase: breaks down sucrose.
  - Lactase: breaks down lactose.
    - Lactose intolerance: inability to digest lactose due to lactase deficiency.
- Poly-, oligo-, disaccharides: complex carbohydrates composed of multiple sugar units.
- Monosaccharides: simple sugars (e.g., glucose, fructose, galactose), the basic units of carbohydrates.
- Transport of monosaccharides: absorbed by enterocytes and transported across the cell membrane.
- Exit of monosaccharides: enter the bloodstream to be used by body tissues.
Proteins:
- Pepsinogen: breaks down proteins in the stomach.
- Pancreatic proteases: continue protein digestion in the small intestine.
  - Trypsin: breaks down proteins.
  - Chymotrypsin: breaks down proteins.
- Carboxypeptidases: remove amino acids from the carboxyl end of proteins.
- Brush border enzymes: complete protein digestion.
  - Aminopeptidases: remove amino acids from the amino end of proteins.
  - Carboxypeptidases: remove amino acids from the carboxyl end of proteins.
  - Dipeptidases: break down dipeptides.
- Amino acids: the basic units of proteins, absorbed by enterocytes and transported into the bloodstream.
Lipids:
- Lipases: enzymes that break down fats.
- Emulsification: bile salts break down fat globules into smaller droplets.
- Digestion with pancreatic lipase: breaks down fat molecules into fatty acids and glycerol.
- Micelle formation: bile salts surround fatty acids and glycerol, allowing for diffusion into enterocytes.
- Diffusion into enterocytes: fatty acids and glycerol enter the enterocytes.
- Chylomicron formation: fatty acids and glycerol are packed into chylomicrons (lipoproteins), allowing for transport through the lymphatic system.
- Lipoprotein lipase: enzyme in the bloodstream that breaks down chylomicrons into fatty acids and glycerol, allowing for delivery to body tissues.
Absorption of vitamins:
- Water-soluble vitamins: absorbed directly into the bloodstream.
- Fat-soluble vitamins: absorbed into the lymphatic system.
Absorption of electrolytes:
- Na+, Cl-, HCO3-: absorbed through different mechanisms.
- K+, iron, Ca2+: absorbed through specialized mechanisms.
Absorption of water: most water is absorbed in the small intestine.

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Test your knowledge on the human digestive system with this quiz. Explore questions about the functions of gastric pits, the role of the pyloric sphincter, and the various components involved in digestion. Perfect for students studying anatomy or anyone interested in how our body processes food.