_____________ digestion occurs within the cell, usually in membrane-bound vesicles.
______________ digestion refers to the digestive process that occurs outside the cell, within a lumen or tract.
Mammals have a one-way digestive tract known as the ________________.
Path of human digestive tract
1. oral cavity
5. small intestine
6. large intestine
The ________________ is where mechanical and chemical digestion of food begins.
_____________ digestion is the breakdown of large food particles into smaller particles through the biting and chewing action (mastication).
While _____________ digestion does not lead to changes in the molecular composition of food, the total surface area of the food is increased, allowing for faster and more efficient enzymatic action
_____________ digestion refers to the enzymatic breakdown of macromolecules into smaller molecules, and begins in the mouth when the salivary glands secrete saliva.
_________ lubricates food to facilitate swallowing, and provides a solvent for food particles.
___________ is secreted in response to a nervous reflex triggered by the presence of food in the oral cavity.
Saliva contains the enzyme ________________ (ptyalin) which hydrolyzes starch into simple sugars.
The tongue manipulates the food during chewing, rolling it into a ball called a ___________, and pushes it into the pharynx.
Chemical rxn of salivary amylase:
starch + H2O --------------------> maltose
The digestive and respiratory passages come together in the _____________.
Food is moved down the esophagus by rhythmic waves of involuntary muscular contractions called _________________.
When a wave of peristalsis spreads down the esophagus, a specialized ring of muscle in the lower esophagus opens, allowing food to enter the stomach. Following the peristaltic wave, this muscle, called the lower ________________, returns to its normal closed state, thus preventing the regurgitation of stomach contents into the esophagus.
lower esophageal sphincter or cardiac sphincter
The walls of the stomach are lined with a thick gastric mucosa containing 2 glands: _________________, _______________.
The _____________ glands of the stomach are stimulated by nervous impulses from the brain, which responds to the sight, taste, and/or smell of food.
The _____________ glands are composed of 3 types of secretory cells: mucous cells, chief cells, and parietal cells.
____________ cells secrete mucus, which protects the stomach lining from the harshly acidic juices present in the stomach.
______________ is composed of the secretions of the chief cells and the parietal cells.
___________ cells secrete pepsinogen, the zymogen of the protein-hydrolyzing enzyme, pepsin.
__________ is the zymogen of the protein-hydrolyzing enzyme, pepsin.
Parietal cells secrete _____________.
______________ facilitates the conversion of pepsinogen to pepsin.
In the stomach, _________ hydrolyzes specific peptide bonds to yield polypeptide fragments.
The ___________ glands secrete the hormone gastrin in response to the presence of certain substances in food.
In the stomach, __________ stimulates gastric glands to secrete more HCl, and also stimulates muscular contractions of the stomach, which in turn churn food.
The low pH of the stomach stops the activity of _______________, which functions optimally at a near neutral pH of saliva.
In the stomach, ___________ is a hydrolytic enzyme that acts on protein to produce peptides.
protein +H2O --------------> peptides
In the stomach, the churning produces an acidic, semi-fluid mixture of partially digested food known as _____________.
At the junction of the stomach and the small intestine is the muscular ________________.
The _________________ regulates the passage of chyme from the stomach into the small intestine via alternating contractions and relaxations.
Although nutrient absorption occurs in the small intestine, alcohol and certain drugs (ex: aspirin) can be directly absorbed into the systemic circulation through capillaries in the stomach wall.
The small intestine is divided into 3 sections in the following order:
duodenum, jejunum, and ileum.
Most digestion in the small intestine occurs in the ________________, where the secretions of the intestinal glands, pancreas, liver, and gall bladder mix together with the acidic chyme entering from the stomach.
The presence of chyme triggers hormonal release, which in turn stimulates and regulates the secretions of the small intestine and its accessory organs.
The majority of nutrient absorption occurs across the walls of the _____________.
Jejunum and the ileum.
The ___________ is a vestigial structure containing lymphoid tissue that is often surgically removed if it becomes infected.
Protein digestion begins in the ____________.
Lipid digestion begins in the _______________.
What is the main function of the large intestine?
reabsorption of water form solid feces/wastes.
In addition to hormonal regulation, the digestive processes are also stimulated by the _______________, and inhibited by the ________________.