AP Lec: Digestive System

What is the primary function of the digestive system?

To break down food into nutrients needed for cell maintenance and growth.

What are the two main groups of digestive organs?

Digestive tract and accessory organs.

What is the digestive tract?

A muscular tube that food passes through, beginning at the mouth and ending at the anus.

What are accessory organs in the digestive system?

Organs that help with digestion by secreting products into the digestive tract, such as salivary glands, liver, gallbladder, and pancreas. Food doesn’t pass through organs.

What is the function of the mesentery?

To attach the digestive tract to the abdominal wall and provide access for blood vessels, nerves, and lymphatic vessels.

What are the four major layers of the digestive tract?

Mucosa (innermost), submucosa, muscular layer, and serosa (outermost).

What is the innermost layer and function of the digestive tract?

Mucosa, responsible for secretion, absorption, and protection.

What is the function of the submucosa?

To support the digestive tract and contain structures involved in supplying and secreting materials.

What is the function of the muscular layer?

responsible for movement and mechanical processing.

What is the function of the serosa?

Outermost protective layer of the digestive tract.

What is the muscular layer of the digestive tract made of?

Smooth muscle with inner circular and outer longitudinal layers.

What is the outermost layer of the digestive tract?

Serosa, except in the oral cavity, pharynx, esophagus, and rectum where it is covered by adventitia.

What are villi in the digestive system?

Small fingerlike projections that increase surface area for nutrient absorption.

What is peristalsis?

A wave of muscle contractions that pushes food forward through the digestive tract.

What is segmentation in the digestive system?

Cycles of muscle contractions that churn and fragment the bolus without moving it in one direction.

What are the six major functions of the digestive tract?

Ingestion, mechanical digestion and propulsion, chemical digestion, secretion, absorption, and defecation.

What occurs during ingestion?

Taking solid food and liquids into the mouth.

What is the role of the oral cavity in digestion?

Mechanical processing, moistening, and mixing food with saliva.

What is the primary function of the stomach?

Chemical breakdown and mechanical processing of food.

What is the primary function of the small intestine?

Enzymatic digestion and nutrient absorption.

What is the role of the large intestine?

Dehydration and compaction of indigestible materials.

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

To manipulate food inside the mouth and aid in digestion.

What is the structure that prevents food from entering the nasopharynx during swallowing?

Uvula.

What are the three regions of a tooth?

Crown, neck, and root.

What is the pulp cavity of a tooth?

The interior chamber of the tooth containing nerves and blood vessels.

What type of epithelium lines the stomach and intestines?

Simple columnar epithelium with goblet cells.

What is the function of the muscularis mucosae?

To change the shape of the lumen and move circular folds and villi.

What are the components of the mucosa?

Epithelium, lamina propria, and muscularis mucosae.

What are the primary stimuli for digestive activities?

Local factors such as changes in pH and physical distortion of the digestive tract wall.

What role do hormones play in the digestive system?

They affect digestive function and are produced by enteroendocrine cells in the digestive tract epithelium.

What is the mineralized matrix similar to bone but contains no cells?

Dentin

What is the interior chamber of the tooth called?

Pulp cavity

What part of the crown is used for crushing, slicing, and chewing?

Occlusal surface

What covers the dentin of the crown?

Enamel

What is the hardest biologically manufactured substance?

Enamel, composed of calcium phosphate

What is the shallow groove surrounding the base of the neck of the tooth?

Gingival sulcus

What covers the dentin in the root of the tooth?

Cement

What structure creates a gomphosis articulation between the root and alveolar bone?

Periodontal ligament

What is the narrow tunnel inside the root of the tooth called?

Root canal

What is the passageway for blood vessels and nerves to the pulp cavity?

Root canal

What are the four types of teeth?

Incisors, Canines, Premolars, Molars

What are incisors used for?

Cutting food

What are canines also known as?

Cuspids

What is the function of premolars?

Crushing, mashing, and grinding food

What is the typical number of roots for molars?

Typically three in the upper jaw and two in the lower jaw

What are deciduous teeth also known as?

Primary, milk, or baby teeth

How many total deciduous teeth are there?

20 total teeth

What are permanent teeth?

Teeth that gradually replace deciduous teeth

What are wisdom teeth?

Third molars that appear on each side of the upper and lower jaws

What is the pharynx?

A membrane-lined cavity behind the nose and mouth

What are the three regions of the pharynx?

Nasopharynx, Oropharynx, Laryngopharynx

What is the function of the esophagus?

Moves food and liquids to the stomach

What prevents air from entering the esophagus?

Upper esophageal sphincter

What is the function of the lower esophageal sphincter?

Prevents stomach contents from flowing backward

What are the three layers of the esophageal wall?

Mucosa and submucosa, Muscularis externa, Adventitia

What initiates the swallowing process?

The buccal phase, which is voluntary

What occurs during the pharyngeal phase of swallowing?

Automatic reflex actions triggered by tactile receptors

What is the function of the peritoneum?

A membrane associated with the abdominal organs

What are the two main layers of the peritoneum?

Visceral peritoneum and Parietal peritoneum

Visceral vs parietal pertioneum

Visceral covers abdominal organs, parietal lines inner surface of the peritoneal cavity

What is chyme?

A viscous, highly acidic, soupy mixture formed in the stomach

What are the four major functions of the stomach?

Temporary storage of food, Mechanical digestion, Chemical digestion, Production of intrinsic factor

What ion is exchanged for chloride in the stomach?

Bicarbonate

How does chloride move into the stomach lumen?

Through chloride channels

What is actively pumped into the stomach lumen using the H+/K+ ATPase?

Hydrogen ions (H+)

What do H+ and Cl- combine to form in the stomach?

Hydrochloric acid (HCl)

What structures in the small intestine increase surface area for nutrient absorption?

Circular folds, intestinal villi, and microvilli

What are circular folds in the small intestine?

Transverse folds along the intestinal lining, mostly found in the jejunum

What are intestinal villi?

Fingerlike projections of the mucosa covered by epithelial cells

What do intestinal glands contain?

Stem cells that produce new epithelial cells and Paneth cells for innate immunity

What is the function of the capillary network in a villus?

Carries absorbed nutrients into the hepatic portal circulation

What is a lacteal?

A lymphatic capillary inside a villus that transports materials that cannot enter blood capillaries

What is the average length of the small intestine?

Approximately 6 meters (19.7 feet)

What is the main function of the duodenum?

Neutralizes acidic chyme and acts as a mixing bowl

What is the primary function of the jejunum?

Majority of chemical digestion and nutrient absorption occurs here

What is the ileocecal valve?

Controls movement from the ileum into the cecum

What are the three major functions of the large intestine?

Reabsorbs water, absorbs vitamins, and stores fecal material

What is the cecum?

An expanded pouch located after the ileum that collects and stores material

What are the four regions of the colon?

Ascending colon, transverse colon, descending colon, sigmoid colon

What triggers the defecation reflex?

Feces entering and distending the rectal wall

What are the three pairs of salivary glands?

Sublingual, submandibular, and parotid glands

What do submandibular glands produce?

Buffers, mucins, and salivary amylase

What is the role of salivary amylase?

Breaks down starch

What is the function of mucous cells in salivary glands?

Secrete mucins, water, and buffers

What is the function of serous cells in salivary glands?

Secrete salivary amylase and lysozyme

What is the average length of the rectum?

Last 15 cm (6 inches) of the digestive tract

What is the role of the teniae coli in the colon?

Help move contents through the colon

What is the composition of feces?

Approximately 75% water, 20% indigestible material, and 5% bacteria

What does the gastrocolic reflex do?

Triggers mass movements in the colon after eating

What are omental appendices?

Small sacs of fat hanging from the colon's outer surface

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

Increases surface area for absorption and contains enzymes that digest materials

Where are the submandibular glands located?

Along the inner surface of the mandible.

What do submandibular glands secrete?

Buffers, mucins, and salivary amylase.

What is the function of salivary amylase?

It breaks down starch.

What percentage of total saliva is produced by submandibular glands?

Approximately 70%.

Where are the parotid glands located?

Inferior to the zygomatic arch.

What type of secretions do parotid glands produce?

Serous secretions containing large amounts of salivary amylase.

What is the primary function of saliva?

To flush oral surfaces, buffer pH, and mix with food to form a bolus.

How much saliva is produced daily?

Approximately 1-1.5 liters.