Digestive system

Major function of the digestive system

Process (digest) consumed food/drink

Alimentary canal (GI tract)

Mouth → Anus

• Digestion & absorption

Accessory digestive organs

Teeth, tongue, salivary glands, gallbladder, liver, & pancreas

• Support actions of GI tract

Peritoneum

Serous membrane of abdominal cavity

Visceral peritoneum

On the external surface of most digestive organs

Parietal peritoneum

Lines body wall

Peritoneal cavity

Fluid lubricates mobile organs

Retroperitoneal organs

Structures posterior to the peritoneum

Intraperitoneal organs

Structures surrounded by peritoneum

Mesentery

Double layer of peritoneum

The Mesentery holds and stores

Organs, fat

The mesentery routes for?

Blood vessels, lymphatics, and nerves

Mucosa and Submucosa overall handles?

Absorption

Muscularis externa overall handles?

Peristalsis (The involuntary constriction and relaxation of the muscles)

Serosa overall handles?

Serous fluid & connection to body walls

Mucosa lines?

Lumen

Functions of Mucosa?

• Secretes mucus, digestive enzymes, and hormones

• Absorbs end products of digestion

• Protects against infection

Submucosa is made with what kind of connective tissue?

Dense irregular

Submucosa maintain?

Blood and lymphatic vessels, and lymphoid follicles

What does the submucosa have to do with the Nerve plexus?

Houses the plexus which controls secretomotor activity and vasomotor activity.

Specific areas of the Submucosa have?

Exocrine glands to provide lubrication and protection

Muscularis Externa is in charge of peristalsis and?

Segmentation

The Muscularis Externa has inner ___ layers and outer ___ layers.

Circular and longitudinal

The Muscularis Externa is controlled by?

Enteric nervous system through the myenteric plexus

Sphincters

Circular layer thickened in some areas in the Muscular externa

Peristalsis

Adjacent segments of the alimentary tract organs alternately contract and relax, and move the bolus along tract

Segmentation

Nonadjacent segments of alimentary tract organs alternately contract and relax, moving food forward, then backward.

What else happens during segmentation?

Food mixing and slow food propulsion happen.

Serosa is made with what kind of tissue?

Areolar connective tissue

The serous membrane connected to?

Visceral peritoneum

Adventitia

Dense collagen layer

The serosa is replaced by adventitia in?

Esophagus, pharynx, mouth, and rectum

Mechanical digestion

• Increases surface area of food

• Muscles, teeth, & bile

Chemical digestion

• Breaks chemical bonds within

molecules

• Stomach acid & digestive enzymes

Oral Cavity

place of taste eval. mastication, lubrication, start of digestion

Hard Palate

Corrugated for tongue friction

Soft palate

Closes off nasopharynx during swallowing (uvula helps too!)

Tongue

Moves food, helps form bolus, swallowing, speech, & taste

Salivary glands

Produce saliva

Bolus

Mass of chewed food

Mechanical digestion involves?

Teeth break up food, increasing surface area

At first humans have?

20 deciduous teeth

Once deciduous teeth fall out then what teeth come in?

32 permanent teeth

When do deciduous teeth fall out?

6-12 yrs of age

What time do 3rd molars usually errupt?

17-25 yrs old

Teeth are covered with?

Enamel

Enamel-producing cells degenerate when..?

Tooth erupts

The decay of enamel producing cells can cause for the tooth to be unable to?

Heal/repair itself

Dental Caries (cavities)

Demineralization of enamel and dentin from bacteria

Gingivitis

Plaque calcifies to form calculus (tarter)

Periodontitis

Destruction/reduction of gums & bone

Chemical digestion involves?

Saliva lubricates food & contains salivary amylase that breaks down polysaccharides

Salivary amylase

Enzyme in human saliva produced by the salivary glands

Parotid

produces salivary amylase (carbs)

Submandibular

Mixture of mucus (buffers, lubricant) and amylase

Sublingual

produces mostly mucus (buffers & lubricant)

Food passes from?

Mouth → oropharynx → laryngopharynx

Step 1 of mouth propulsion

Buccal phase

Step 2 of mouth propulsion

Pharyngeal phase

Step 3 of mouth propulsion

Esophageal phase

Step 4 of mouth propulsion

Bolus enters stomach

Esophagus is how long?

25cm or 10in

Esophageal hiatus

allowing the esophagus to pass from the thorax into the abdomen

Esophagus joins stomach at?

cardiac orifice/sphincter

cardiac orifice/sphincter

The opening where the esophagus joins the stomach, located behind the 7th left costal cartilage

Gastric folds (rugae)

longitudinal folds of the mucosa and submucosa layers in the stomach that allow it to expand and increase volume, accommodating food without increasing pressure

Stomach has how many muscle layers?

3

3 regions of the stomach

Cardiac, Fundus, and body

What controls entry of chyme into duodenum?

Pyloric sphincter

Mucosa

Mucus membrane

• Simple columnar epithelium

Gastric pits

Gateways to gastric glands

Gastric glands

Create gastric juice