Digestive I Flashcards
What is the primary function of the digestive system?
move nutrients, water and electrolytes from the external environment into the body’s internal environment
The digestive system is central to regulation and integration of _______ processes throughout the body
and proper functioning necessary for whole-body __________
metabolic, homeostasis
The digestive system extends from ______
to the _____ intestine (~15 ft length in live person)
mouth, large
___ _____: a long tube with muscular walls lined by transporting and secretory epithelial cells
GI tract
Stomach to the anus = ___
GUT
________: mechanical and chemical breakdown of food primarily occurs in the gut (breakdown of macromolecules into smaller substances that can be transported across the epithelial cell layer
Digestion
The digestive system is joined by secretions from accessory glandular organs like the ______ ______, _____, ________, and ________
salivary glands, liver, gallbladder, pancreas
Technically GI tract is continuation of ______ environment (bacteria)
external
A lot of those bacteria in the large intestine serve functions that help us:
- breaking down certain _____ compounds
- creating certain _______
- releasing _________ into the body that are important in many processes like modifying the nervous system, angiogenesis, promoting the storage of fat, etc
food, vitamins, substances
____ refers to structures in the abdominal cavity, stomach down, most of digestion occurs here
Gut
Digestion begins in the mouth with ________ (chewing) and the addition of _____. Tongue and lips also helps manipulate food
mastication, saliva
Three pairs of salivary glands: ?
Parotid – at the hinge point of your jaw
Sublingual – under the tongue
Submandibular – along the mandible
Three pairs of salivary glands with multiple functions: ?
- Moisten and lubricate food
- Amylase partially digests polysaccharides
- Dissolve some food molecules (taste)
- Lysozyme kills bacteria
__________ also exist in the saliva
Immunoglobins
_______: passageway from mouth to stomach
-upper and lower esophageal sphincters
Esophagus
Esophagus wall: top 1/3 is ______ muscle, bottom 2/3 ______ muscle
skeletal, smooth
Esophagus moves food via _______ waves
peristaltic
Digestion continues in stomach, mixing food with acid and enzymes to create _____
chyme
What are the 3 main sections of the stomach (starting at the esophagus)?
Fundus, Body, Antrum
What and where is the pylorus?
At the end of the antrum, it is a valve/sphincter
_____ esophageal sphincter relaxes during swallowing
_____ esophageal sphincter permits the movement of food from esophagus into the stomach and prevents backflow
Upper, Lower
Majority of digestion and absorption takes place here ?
Small intestine
What are the 3 main portions of the small intestine (starting from the stomach)?
Duodenum (first 25cm)
Jejunum
Ileum
Liver and pancreas release exocrine secretions into the _______ (there’s another sphincter here that does this)
duodenum
What are the 5 main portions of the Large intestine (starting from the ileum)?
Cecum - initial pouch
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Feces entering the terminal section of the large intestine (rectum) trigger a __________ reflex
defecation
______ ________: 1.5 L of watery chyme pass into here each day; water and electrolytes removed to create semisolid feces
Large intestine
Basic structure of GI wall is similar in both the stomach and intestines with ______ variations from one section to another
slight
The four main GI layers:
mucosa, submucosa, muscularis externa, serosa
Starting from the lumen, it goes to mucosa, which is made up of three separate layers: ?
epithelial, lamina propria, and muscularis mucosa, not the normal muscle for digestion
Then we have the submucosa (contains the submucosal ______), next is the major muscle layer: muscularis ________.
plexus, externa
Finally, we have a dense connective tissue layer surrounding the entire outside of the GI tract called the _______.
serosa
Within the muscularis externa, we have another plexus (nerve network) known as the _________ plexus
myenteric
Enteric is technically under peripheral but what is different is that the ENS can function ________, it does not need input from the CNS to function. It does receive input but it can function normally without to some degree
autonomously
The _________ plexus – tends to influence the mucosal layer and the epithelial cells
The _________ plexus – tends to influence the muscle as well as communicate with the submucosal plexus
submucosal, myenteric
Mucosa is divided into 3 further layers:
- The _________: the layer that lines the single layer of cells that lines the innermost portion. A variety of different cells exist in the epithelium which facilitates the transport of substances from the lumen into the interstitial fluid and into the blood vessels
- _______ ______: connective tissue layer, largely contains interstitial space as well as vasculature (small blood vessels) and small lymph vessels
- _______ ______: not the normal smooth muscle layer, thin layer of smooth muscle that believes to influence the amount for surface area available for absorption
epithelium, Lamina Propria, Muscularis Mucosa
Gastric folds increase surface area: ______
Rugae
In the stomach, surface area is increased by invagination called _______ _______
gastric glands
Intestinal surface area is enhanced by fingerlike villi and invaginations called _____
crypts
______ further increase surface area
Plicae
_____ increase surface area so that you can absorb large amounts
Villi
There are also gastric glands contain a large number of cells that are responsible for _______ secretion and _________ secretion
exocrine, endocrine
Epithelium changes depending on the _______ of the GI tract
region
Most transport is ________, but there are areas where there is higher amount of _________ transport
transcellular, paracellular
Massive turnover in epithelial cells in the GI tract due to constantly being exposed to _____ _______
harsh substances
Epithelium (most variable):
- Include transporting epithelial cells, endocrine and exocrine secretory cells
- Junctions very _____ in stomach and colon, ______ in small intestine
- _______ lifespan (a few days) GI stem cells constantly producing new cells.
tight, leaky, Short
The epithelium alternates between many kinds of cells including simple columnar epithelium with microvilli and _________ _____
enteroendocrine cells
Lamina propria
Subepithelial tissue containing _____ fibres, small _____ vessels and _____ vessels
nerve, blood, lymph
Muscularis mucosae
Thin layer of ________ muscle that can alter the surface area available for ________
smooth, absorption
____________: middle distensible layer containing larger vessels (lymph and blood) and the submucosal plexus; one of the major nerve networks in the enteric nervous system
Submucosa
Submucosa is another layer of connective tissue that is relatively ________ (loose)
distensible
_______ _____: 2 or 3 layers of smooth muscle: circular decrease diameter, longitudinal shortens the tube. Contains myenteric plexus
Muscularis externa
_______: outer covering of connective tissue that is a continuation of the peritoneal membrane, sheets of mesentery hold intestines in place
Serosa
These are the four basic functions and processes of the GI tract: ?
Digestion, Secretion, Absorption, and Motility
Secretion can mean a few different things in the Gi tract:
1. It can mean the movement of substances from the ____ into the ______ (classic secretion)
2. It can also be the movement of substances that are produced in ________ cells into the lumen
ECF, lumen, epithelial
Motility is necessary for _________ digestion
mechanical
3 main challenges of the digestive system: ?
avoiding autodigestion, defense, and maintaining mass balance
________ _______: breaking food down into small enough molecules to be absorbed without digesting the cells of the GI tract
Avoiding autodigestion
_______: absorbing water and nutrients while preventing bacteria, viruses and other pathogens from entering the body. Mechanisms to help with this defense include mucus, digestive enzymes, acid and the largest collection of lymphoid tissue
Defense