Week 7 - Digestive System Flashcards
What is the difference between peristalsis and segmentation?
- Peristalsis involves the contraction of longitudinal muscles
- Segmentation involves the contraction of circular muscles
Why is the oral cavity line with stratified squamous epithelium?
Allows it to withstand friction and abrasion of eating
How do the lips and cheeks aid in the mastication of food?
Help keep food in between the teeth as we chew
Differentiate between the hard and soft palate of the mouth
- Hard palate - forms a hard surface which food can be forced against when chewing.
- Soft palate - closes of the nasal passages during swallowing
What accessory organ of the mouth is used in the process of mastication?
Teeth
What is bolus?
Is the mixture of food and saliva that forms during chewing
What kind of muscle is the tongue made of?
Skeletal muscle
What are the 2 functions of the tongue?
- Speech
* Taste
What role does saliva play in the digestive processes of the mouth?
- Contains enzymes that begin the break down of starch
- Helps moisten food and create bolus
- Cleanses the mouth
What two regions of the pharynx are involved in digestive system activity?
- Nasopharynx - N/A
- Oropharynx
- Laryngopharynx
What are the 4 steps associated with digestion in the mouth?
1) ingestion
2) chemical digestion - amylase
3) mechanical digestion - teeth
4) swallowing of food into the pharynx
What are the two phases associated with swallowing?
- Buccal - voluntarily pushing food into pharynx
* Pharyngeal / oesophageal - involuntarily swallowing of food into the oesophagus.
Describe the basic function of the stomach
- Intake of food from the oesophagus
- Temporary storage of food
- Digestion of food via enzymes and mechanical digestion
- Moves chyme into the duodenum
What separates the stomach from the duodenum?
Pyloric sphincter
What cells make up the gastric glands? What are their functions?
- Parietal cells - Secrete HCl
- Mucous neck cells - unkown
- Chief cells - secrete lipases
- Enteroendocrine cells - secrete hormones that aid in digestion
Name the three phases of gastric secretion
- Cephalic phase
- Gastric phase
- Intestinal phase
What is the stimulus for the cephalic phase of gastric secretion?
• Sight, taste, thought or smell of food
What is the purpose of the cephalic phase of gatric secretion?
To prepare the stomach for the arrival of the bolus
What initiates the gastric phase of gastric secretion?
Neural and hormonal stimuli that occurs once the food has entered the stomach
What initiates the intestinal phase of gastric secretion?
The low pH of the duodenum as chyme enters small intestines
What is chyme?
Is the fluid that passes form the stomach into the small intestines, consisting of gastric juices and partially digested food
What is the purpose of the intestinal phase of gatric secretion?
To secrete more gastric to have a brief effect and then to inhibit the secretion of gastric juices.
What are the three different contractile activities of the stomach? Exlpain
- Propulsion -peristaltic contraction that move contents towards the pylorus
- Grinding - Mixing of the stomach contents
- Retropulsion - Delivers small amount of chyme into the duodenum.
What is the role of the liver in the digestive system?
The liver produces bile
Where does bile enter the GI tract?
duodenum
What is the function of the gall bladder?
Stores and concentrates bile produced from the liver that is not immediately needed
What role does bile play in the digestive process?
emulsifies fats
Where is pancreatic juices secreted?
duodenum
What gives pancreatic juices its alkaline pH and what is its function?
Bicarbonate ions which help the neutralise the acidic contents of the stomach as it enters the duodenum.
Amylases break down ________?
Carbohydrates
Proteases break down _________?
Proteins
Lipases break down __________?
Lipids
Nucleases break down __________?
Nucleic acids
Name the three sections of the small intestines
- Duodenum
- Jejunum
- Ileum
What separates the small and large intestines?
ileocecal valve
What are the 4 layers of the small intestines and their respective function
- Serosa - secrete serous fluids
- Muscularis externa - segmentation and peristalsis
- Submucosa - supports mucosa and binds the mucosa to the underlying smooth muscle
- Mucosa - secretes digestive enzymes
What are the three structural modification in the small intestines that increase absoprtion in the small intestines?
- Circular folds of the mucosa and submucosa
- Villi - increase SA
- Microvill - Increase SA and contain brush border enzymes
What region of the GI tract is responsible for the majority of absorption?
Small intestines
What is the function of segmentation in the small intestines?
Ensures that the chyme is thoroughly mixed so that maximum absorption can take place.
What do chief cells release?
pepsinogen
What do parietal cells release?
HCl
What activates pepsinogen to _______?
HCl activates it to pepsin
What molecules does pepsin act on?
proteins
During the absorptive state ______ exceeds ______?
Anabolism exceeds catobolism
During the Post-absorptive state ______ exceeds _____?
Catabolism exceeds anabolism
What cells in the pancreas produce insulin?
Beta cells
What cells in the pancreas produce glucagon?
Alpha cells
