A&PII Exam 3

Two groups of organs for the digestive system

Gastrointestinal tract and accessory digestive organs

Gastrointestinal (GI) tract (alimentary canal) consists of

mouth, most of the pharynx, esophagus, stomach, small intestine, and large intestine

Accessory digestive organs

teeth, tongue, salivary glands, liver, gallbladder, and pancreas

Functions of Digestive System

1. Ingestion of foods and liquids

2. Secretion of -7L/day of water, acid, buffers, and enzymes into the lumen by lining of digestive tract and accessory organs

3. Mixing and propulsion

4. Digestion

5. Absoption

6. Defecation

Mixing and propulsion

alternating contraction and relaxation of the wall of smooth muscle in digestive organs, also aids in motility to mix and propel food

Digestion

breakdown of food into smaller pieces

Absorption

uptake of nutrient molecules into the epithelial cells of the digestive tract and then into the blood and the lymph

Defecation

elimination of feces this includes wastes, bacteria, indigestible substances, cells from the GI lining and materials that are not absorbed

Layers of the GI tract

mucosa, submucosa, muscularis, and serosa

Mucosa is the

inner lining

Mucosa consists of

epithelium, lamina propria, muscularis mucosae

Epithelium

protection, secretion, absorption

Muscularis mucosae makes

folds that helps to increase surface area

Submucosa is the

connective tissue binding mucosa to muscularis

Muscularis

voluntary skeletal muscle found in mouth pharynx and upper ²/₃ of the esophagus and anal sphincter

Serosa (visceral peritoneum)

outermost covering of organs suspended in the abdominopelvic cavity

Enteric Nervous System (ENS)

intrinsic set of nerves extending from esophagus to anus (part of the ANS)

ENS contains

submucosal plexus and myenteric plexus

Submucosal plexus

controlling secretions

Myenteric plexus

GI tract motility

Myenteric plexus is located between the

longitudinal and circular smooth muscle

Autonomic Nervous System (ANS)

extrinsic set of nerves that regulate the ENS

parasympathetic ENS

when stimulated increases secretion and activity by stimulating ENS

sympathetic ENS

when stimulated decreases secretion and activity by inhibiting the ENS

Peritoneum

largest serous membrane in the body

Parietal peritoneum

lines the wall of cavity

Visceral peritoneum

touching the organs

5 major peritoneal folds

greater omentum, falciform ligament, lesser omentum, messentary, and the mesocolon

The 5 major peritoneal folds functions

bind organs together and provide a path for blood and lymph vessels

Lesser omentum

suspends stomach and duodenum from liver

Mesocolon

bind colon to posterior abdominal wall

Mesentery

bind small intestine to posterior abdominal wall

Greater omentum

“fatty apron”, drapes over intestines

Falciform ligament

attaches liver to anterior abdominal wall and diaphragm

Mouth (oral or buccal cavity) extends from

gums and teeth to fauces

Uvula and soft palate

close off the nasal cavity during swallowing

Salivary glands secrete

most of the saliva in the mouth

Salivary glands

parotid, submandibular, and sublingual glands

Saliva is mostly

water 99.5%, 0.5% solutes

Solutes in saliva

ions, dissolved gases, urea, uric acid, mucus, immunoglobulin A, lysozyme, and salivary amylase

Tongue is made of

skeletal muscle that is covered by a mucous membrane

Tongue maneuvers

food while chewing, shaping food, and pushes food to back of mouth

Teeth found within

gingivae (gums)

Crown

visible portion. made of dentin and enamel

Neck of teeth

between crown and root

Root of teeth

embedded within gums

Esophagus

secretes mucus and transports food

Esophagus does not

produce enzymes nor absorbs

Esophagus consists of

mucosa, submucosa, and muscularis (superior 1/3 skeletal muscle, middle 1/3 skeletal and smooth muscle, and inferior 1/3 smooth muscle)

Upper esophageal sphincter

regulates movement of food into esophagus

Lower esophageal sphincter

Regulates movement from esophagus to the stomach

Adventitia

attaches esophagus to surroundings

Stomach

mixing chamber and holding resevoir

Four main regions of the stomach

cardia, fundus, body, and pylorus

Mucosa of stomach contains

mucosa neck cells, parietal cells, chief cells, G cells, submucosa, muscularis, and serosa

Mucous neck cells produce

mucous and protect stomach

Parietal cells secrete

hydrochloric acid

Muscularis in the stomach has a

additional 3rd inner oblique layer

Exocrine

glands that secrete into ducts

Endocrine

Ductless glands secrete into blood stream

Pancreas

secretes pancreatic juice which is secreted by exocrine glands; bicarbonate juice that neutralizes the acidity of chyme in the small intestine

Pancreas lies posterior to the

greater curvature of the stomach

99% of the pancreas are

acini that secrete pancreatic juice

1% of the cells are

pancreatic islets (islets of Langerhans)

Islets of Langerhans are

endocrine cells that secrete hormones

Liver

heaviest gland of the body

Falciform ligament

connects the two lobes of the Liver

Hepatocytes secrete

bile (800-1000mL/day)

Hepatocytes make up

80% of liver’s weight

Bile canaliculi collects

bile

Hepatic sinusoids

fenestrated blood capillaries that are fixed macrophages

Hepatic laminae

make the liver look like wagon wheels

pH of bile

7.6-8.6

Bile consists of

water, bile salts, cholesterol, phospholipid lecithin, bile pigments, and several ion

Bilirubin

principle bile pigment (when RBCs are broken down)

Bile salts play an active role in

emulsification

Emulsification

the breakdown of large lipid globules into a suspension of small lipid globules

Functions of the liver

1. Secretion of bile

2. carbohydrate metabolism

3. Lipid metabolism

4. Protein metabolism

5. Processing of drugs and hormones

6. Excretion of bilirubin

7. Synthesis of bile salts

8. Storage of vitamins and minerals

9. Phagocytosis of old RBCs

10. Activation of vitamin D

Gallbladder

stores and concentrates bile produced by liver

Small intestine

most digestion and absorption occurs

Small intestine is made of

Duodenum, Jejunum, and Ileum

Absorptive cells (in the small intestine)

digest and absorb

Goblet cells (in the small intestine)

produce mucus

Intestinal glands (in the small intestine)

produce intestinal juice

Paneth cells (in the small intestine)

produce antimicrobial proteins

Muscularis (in the small intestine)

inner circular layer: thicker and outer longitudinal layer: thinner

Small intestine wall contains

circular folds, villi, and microvilli

Large intestine completes

absorption, produce certain vitamins, and form and expel feces

Four main region of large intestine

cecum, colon, rectum, and anal canal

illeocecal sphincter

between small and large intestine

Colon separated into

ascending, transverse, descending, and sigmoid

Internal anal sphincter

smooth muscle

external anal sphincter

skeletal muscle

Muscularis longitudinal layer of the large intestine if modified to form

teniae coli

Mechanical digestion starts in the

mouth (chewing)

Bolus

lump of soft food that is easy to swallow

Bolus is pushed to back of mouth by

tongue, food passes to pharynx

Epiglottis blocks

trachea

Upper esophageal sphincter opens allowing

food to pass into esophagus

Upper esophageal sphincter close as food travels

down esophagus to stomach passing through lower esophageal sphincter