! BIOL 1410 Digestive system

LECTURE 15

What is the Gastrointestinal (GI) tract?

Tube from mouth to anus

What are the accessory organs in the mouth?

Teeth, tongue, salivary glands

What are the (3) main accessory organs?

Pancreas, liver, gall bladder

What are the (4) digestive processes (beginning with ingestion)?

Ingestion, digestion, absorption, defecation

Define ingestion

Food into the oral cavity

Define digestion

Large molecules broken into smaller molecules

What are the two types of digestion?

Mechanical + chemical

Define absorption

End products of digestion enter blood or lymph

Define defecation

Elimination of undigested material

What are the 4 initial structures of the digestive system?

Oral cavity, salivary glands, dentition (teeth), oropharynx/laryngopharynx

What 3 things are included in the oral cavity?

Lips, cheeks, palate

Which palate is posterior to the other (hard/soft)?

Soft: posterior to hard

What type of muscle is the soft palate made of?

Skeletal muscle

What material is the hard palate made of?

2 maxillae + 2 palatine bones

What is the posterior projection of the soft palate called?

Uvula

When does the uvula rise to close what?

To close nasopharynx when swallowing

What bone is the tongue attached to?

Hyoid bone

What type of muscle is the tongue made of?

Skeletal muscle

What are papillae on the tongue?

Projections of mucosa (taste buds)?

What are the 3 pairs of salivary glands?

Parotid, submandibular, sublingual

Which pair of salivary glands are inferior + anterior to the ears?

Parotid gland(s)

What are mumps?

Inflammation of 1 or both parotids

Which pair of salivary glands is found in the floor of the mouth?

Submandibular gland(s)

What is the composition of saliva?

99.5% water, 0.5% solutes

What are the two types of dentition?

Child/primary dentition, adult/secondary dentition

How many premolars do children vs. adults have (in each quadrant)?

Child (0), adult (2)

How many molars do children vs. adults have (in each quadrant)?

Child (2), adult (3)

How many total teeth do children vs. adults have?

Child (20), adult (32)

What are the 5 components of tooth structure?

Crown, root, neck, periodontal ligaments, root canal (→ pulp cavity)

What 2 tissues are found at the crown of the tooth above the gum?

Dentin + enamel

Which tissue covers the majority of the tooth?

Dentin

Which tissue is the overlay of the crown of the tooth?

Enamel

What are the (3) important key features of enamel?

Acellular, highly calcified, hard

What tissues overlay the root of the tooth?

Dentin + cementum

Dentin, enamel and cementum are similar to bone, but have what difference?

Avascular (while bone is highly vascular)

What 2 tissues (specific to dentition) is the neck of the tooth composed of + where is it the neck of the tooth located?

Composed of enamel + cementum, boundary at the gums between the crown and root

What do the periodontal ligaments do?

Attach root to bones

What is contained in the root canal (extending into the pulp cavity)

CT, blood/lymph vessels, nerves

What 2 tissue types is the oropharynx and laryngopharynx made of?

Muscularis externa (skeletal muscle) + stratified squamous epithelium

What are the 4 basic layers of the GI Tract (inner → outer)?

Mucosa, submucosa, muscularis externa, serosa

What are the 3 sublayers of the mucosa (inner → outer)?

Epithelium, lamina propria (areolar CT), muscularis mucosa

What type of glandular cells are concentrated in the epithelial layer of the mucosa?

Goblet cells

What two subtypes of epithelial tissue are found in the GI Tract?

Stratified squamous + simple columnar

The GI Tract is very long, and the epithelial tissue differs depending on the location you are observing. In what 2 places is the stratified squamous epithelium?

Esophagus + anal canal

The GI Tract is very long, and the epithelial tissue differs depending on the location you are observing. In what ~4 places is the simple columnar epithelium?

stomach, small/large intestines, rectum

Reminder: What is lamina propria?

Loose areolar CT

What is contained in the lamina propria layer of the mucosa?

Blood, lymph vessels, lymph nodules/tissues (immune)

What does the muscularis mucosa (smooth muscle layer of mucosa of the GI Tract) allow for?

Movement of mucosa

What major/subtype tissue is the submucosa layer of the GI Tract composed of?

Loose areolar CT

What is contained in the submucosa layer of the GI Tract?

Blood, lymphatic vessels, network of nerve cells

Muscularis externa of the GI tract is _ layers of smooth muscle, separated by what?

“2,” Separated by 2nd network of nerve cells (2nd after previously mentioned submucosa)

The inner circular layer of muscularis externa constricts the lumen by __________

“contraction”

The outer longitudinal layer of the muscularis externa contracts, which shortens ___ ______

“gut length”

Overall, the contraction of the muscularis externa causes what?

Motility (mixing + movement)

The outer layer (farthest from lumen) of the GI Tract is serosa/adventitia. What is a key defining feature of its membrane?

It has a double-walled membrane

The cavity of the GI Tract where substances pass through is called?

Lumen

What is the peritoneum?

The serous membrane that lines the abdominopelvic cavity + most of the abdominal organs

What are the 2 layers of the peritoneum?

Parietal and visceral

Which peritoneum layer is against the organ wall, and which is against the abdominal cavity wall?

Visceral (organ wall), parietal (abdominal cavity wall)

What is the peritoneal cavity of the peritoneum?

Space between peritoneum layers (visceral/parietal)

What fluid is contained within the peritoneal cavity?

Serous fluid

What are the 2 specializations (folds of serosa) of the peritoneum?

Omenta, mesentery

The omenta is folds of serosa between what structures?

Organs

The omenta is a sheet of 2 fused layers of _______ peritoneum

“visceral”

What does the omenta contain?

Blood/lymph vessels + nerves

The omenta is subdivided into what 2 sections?

The greater and lesser omentum

Which omentum (greater/lesser) is the “fatty apron”?

Greater omentum

What structures does the greater omentum connect?

Stomach → transverse colon

The greater omentum forms a large fold that hands down over what 2 structures?

Transverse colon + small intestine

What structures does the lesser omentum connect?

Liver → stomach

The mesentery is folds of serosa between what specific structures?

Posterior abdominal cavity wall + small/large intestines

The mesentery is a sheet of 2 fused layers of _______ peritoneum

“parietal”

The mesentery is an entry/exit point for what structures?

Blood vessels, nerves, lymphatic vessels (that specifically supply digestive organs)

Where are the retroperitoneal organs located?

Posterior to the parietal peritoneum

The peritoneum only lines the _______ side of retroperitoneal organs

“anterior”

What is an example or two of a retroperitoneal organ?

E.g. pancreas, duodenum

What is the posterior side of a retroperitoneal organ lined by?

CT (adventitia)

Which is posterior to the other; esophagus or trachea?

Esophagus is posterior to trachea

The esophagus passes through the diaphragm to the _________ cavity

“abdominal”

What are the 2 components of the histology of the esophagus (superior → inferior)?

Muscularis externa, adventitia/serosa

The muscularis externa of the esophagus is divided into 3 sections based on the type of muscle it contains. From the upper 1/3 to the lower 1/3, list the muscle type(s) of these layers.

Upper 1/3 (skeletal), middle 1/3 (skeletal/smooth), lower 1/3 (smooth)

Of the adventitia/serosa layer of the esophagus, which is the outer layer?

Adventitia

Of the adventitia/serosa layer of the esophagus, one is within the thoracic cavity and one is within the abdominal cavity. Which is which?

Adventitia (thoracic), serosa (abdominal)

The stomach stores, partially digests, and regulates the emptying of what substance?

Chyme (food + gastric juice)

Chyme moves from the stomach to what structure?

The small intestine

What are the 4 regions of the stomach?

Cardiac region (cardia), fundus, body, pyloric region (pylorus)

Which stomach region is attached to the inferior esophagus?

Cardiac region (cardia)

Which stomach region is superior to the esophageal entrance?

Fundus

Which stomach region is the middle portion?

Body

Which stomach region is the inferior portion?

Pyloric region (pylorus)

What does the pyloric sphincter (within the pyloric region) regulate?

Regulates release of stomach contents into small intestine

What are the 3 components of the histology of the stomach?

Mucosal surface, rugae, muscularis externa

The mucosal surface of the stomach is exclusively formed by what cells?

Mucous cells

What does the mucosal surface have millions of?

Gastric pits

What are gastric pits?

Invaginations (surface folding inward to form a pocket) of epithelium

What are gastric pits of the stomach connected to?

Underlying gastric glands

What are gastric glands (exocrine or endocrine/secretion)?

Exocrine glands, secrete gastric juice into gastric pits (then enters stomach lumen)

What 4 types of cells are contained in gastric glands?

Goblet cells, chief cells, parietal cells, G (enteroendocrine) cells

Chief cells secrete enzymes for digestion of specifically what 2 macromolecules?

Protein + fat

What do parietal cells secrete to lower stomach pH?

Secrete hydrochloric acid (HCl)