Digestive System - A&P II

to process and sequester energy and essential nutrients from what we eat

digestive system function

what are the two main divisions of the digestive system

alimentary canal and accessory organs

organs that food or waste pass through

alimentary canal

organs that secrete substances that aid the digestive process

accessory organs

list the accessory organs from superior to inferior

teeth and tongue, salivary glands, gall bladder, liver, pancreas

list the alimentary canal organs from superior to inferior

mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus

medical term for eating

ingestion

medical term for propulsion

peristalsis

physically breaking up food

mechanical digestion

chemically breaking down food

chemical digestion

getting digested nutrients into the blood

absorption

removing waste products from the body

defecation

what kind of sensors are present in the walls of the alimentary canal

mechanoreceptive and chemoreceptive sensors

sensors that monitor the stretch of the alimentary canal

mechanoreceptive sensors

sensors that monitor the pH and chemical environment within the alimentary canal

chemoreceptors

movement of food or waste through the system

peristalsis

stimulation of receptors within the alimentary canal causes changes in…

hormone release and peristalsis

what are the two main influences on the gut

intrinsic and extrinsic

a plexus of nerves in the wall of the GI tract allow organs to communicate and coordinates physical digestion

gut brain (intrinsic gut influence)

hormones secreted by the stomach and small intestine that will affect other digestive organs

extrinsic gut influences

membrane of connective tissue

peritoneum

surrounds abdominal organs

visceral peritoneum

lines inside of abdominal cavity

parietal peritoneum

houses organs and produces peritoneal fluid

peritoneal cavity

allows organs to move easily during digestion

peritoneal fluid

bacteria from a burst appendix leak into the abdominal cavity causing infection and inflammation

appendicitis → peritonitis

what is the treatment for appendicitis/peritonitis

lavage and antibiotics

double layer of peritoneum that extends from the digestive organs to the parietal peritoneum

mesentery

provides a pathway for blood vessels and nerves to reach digestive organs

mesentery function

blood supply of the intestines

splanchnic circulation

True or false: although splanchnic circulation serves the intestines, it never travels through the mesentery

false

innermost layer of epithelium

mucosa

secretes mucus and digestive enzymes, and provides barrier to pathogens and enzymes

mucosa

muscle layer of the alimentary canal that produces muscle contractions for peristalsis

lamina muscularis mucosae

is the muscle in the alimentary canal smooth or skeletal

smooth

briefly describe the histology of the alimentary canal

lined with mucus and largely composed of muscle

elastic, innervated, highly vascular connective tissue

submucosa

smooth muscle layer responsible for segmentation and peristalsis

muscularis externa

outer covering of connective tissue

serosa (visceral peritoneum)

palatine bones in skull

hard palate

digestion begins in..

your mouth

mostly skeletal muscle, rises to close nasopharynx during swallowing

soft palate

interlacing bundles of muscles that grip and taste food and assist in mechanical digestion

tongue

add roughness to the tongue and house taste buds

papillae

what is unique about the tongue musculature

it has an origin point but no insertion point to allow it to be really flexible and mobile

true or false: the tongue is the strongest muscle in the body

false

produces saliva

salivary glands

moistens food, begins digestion, dissolves chemicals, cleanses the mouth

saliva function

what does saliva digest

complex carbs via amylase

saliva contains…

enzymes, electrolytes, and immune-related chemicals (lysozyme, defensin, mucus, antibodies)

salivary gland located under the tongue

sublingual gland

salivary gland located posterior to masseter muscle

parotid gland

salivary gland located under mandible

submandibular gland

list the salivary glands

sublingual, parotid, and submandibular

other than the salivary glands, saliva is secreted by the … scattered throughout the oral cavity

buccal glands

food ingestion __ salivation

increases

briefly describe how salivation happens

mechano- and chemoreceptors in the brain send messages to the salivatory nuclei in the brain to increase salivation rates

other than food ingestion, what can increase salivation

neural input (smells, descriptions of food, Pavlov’s dogs, etc.)

muscular tube that is superior to the stomach

esophagus

serves to propel food into the stomach via peristalsis

esophagus function

the passage of food through the esophagus is easy by…

lubricating mucus secreted from the submucosa

the esophagus joins the stomach at the…

gastroesophageal sphincter

keeps the stomach contents in the stomach

gastroesophageal sphincter

the result of gastric juice moving past the gastroesophageal sphincter and into the stomach

heartburn

true or false: the stomach is very elastic

true

how can the stomach stretch so much

rugae (folds) that stretch when food enters

attaches the curvatures of the stomach to the parietal peritoneum; holds stomach in place

omentum

how does the stomach perform mechanical digestion

contains muscles that go in different directions (longitudinal, circular, oblique)

prevents stomach contents from prematurely entering the small intestine

pyloric sphincter

list the two sphincters of the stomach from superior to inferior

gastroesophageal and pyloric

produce gastric juices

gastric glands

gastric gland that produces acidic mucus (function not yet known)

mucus neck cells

gastric gland that secretes HCl and intrinsic factor

parietal cells

gastric gland that gives the stomach contents a pH between 1.5 and 3.5

HCl

intrinsic factor is essential for…

vitamin B12 absorption and RBC production

gastric gland that produces pepsin in the acid of the stomach

chief cells

acid/enzyme that breaks down proteins in the stomach

pepsin

gastric gland that releases hormones that regulate gut function; e.g. gastrin

enteroendocrine cells

why does the stomach produce acid AND enzymes

acid denatures proteins while enzymes break proteins into individual amino acids

HCl denatures proteins into simpler shapes, making it easier for enzymes to…

catabolize them

becomes pepsin in stomach acid

pepsinogen

enzyme that degrades milk proteins in infants

rennin

sensory input from nose, eyes, thoughts, etc. increase gastric secretion rates

cephalic reflex

distension of stomach (stretch), partially digested proteins, and increases in pH stimulate secretion

gastric stimulus

when intestines receive processed food from the stomach (chyme), the pyloric sphincter closes and decreases gastric secretion rates

intestinal stimulus

list the ways gastric secretion is regulated

cephalic reflex, gastric stimulus, intestinal stimulus

serves to mix food and create chyme

motility

stomach moves food inferiorly (from gastroesophageal sphincter to the pyloric sphincter) via…

peristalsis

only small amounts of … are allowed into the small intestine by the pyloric sphincter

chyme

more stretch (more food) = …

more mixing

caused by gastric irritants (bacteria, alcohol, alkaloids, etc.) as well as psychological stimuli

vomiting

describe what happens during vomiting

coordinated reflex action of muscles (diaphragm and abdominal wall), soft palate closes off nasopharynx (most of the time) and gastroesophageal sphincter (opens to esophagus)

digestion is completed here after receiving the chyme from the stomach

small intestine (SI)

extends from the pyloric sphincter of the stomach to the ____, where the SI joins the LI

ileocecal valve

true or false: the small intestine is larger after death because there is no longer any muscle tone

true

why is the small intestine so long?

to allow enough time and surface area for absorption of nutrients

receives chyme from the stomach, bile from the liver, and pancreatic juice

duodenum

list the small intestine (SI) divisions from superior to inferior

duodenum, jejunum, ileum

bile and pancreatic juice are controlled by the…

hepatopancreatic sphincter

extends from the duodenum to the ileum

jejunum