Digestive System And Metabolism Flashcards
The digestive system goes from the oesophagus to the anus and is composed of four layers which are?
- Mucosa: inner layer of mucous membrane
- submucosa: supporting layer of connective tissue
- muscularis externa: double layer smooth muscle
- Serosa: outer layer of serous membrane
The surface of the small intestine is designed to enhance absorption. How?
Circular folds: deep folds slow the progress of chyme
villi and micro-villi: increase surface area and produce brush border enzymes to complete digestion of carbs and protein
Metabolism is the way in which nutrients are altered or changed for use by the body. What are the 2 types of metabolic processes?
Anabolism: any process in which larger molecules are built from smaller ones (synthesising and building)
Catabolism: any process that breaks down complex structures into more simple structures (degenerate and breakdown)
What is the basal metabolic rate? (BMR)
The measurement of the energy required for the body to perform only it’s most essential activities
Where does urine travel from and what does it travel through to exit the body?
Kidneys 👉 ureters 👉 bladder 👉 urethra
What is the definition of an acid?
Acids are buffers within the blood to maintain pH levels and are excreted to maintain acid base balance
Define glycogenesis
Formation of glycogen (ie, long chains of glucose molecules).
Define glycogenolysis
The breaking down of glycogen stores when blood glucose levels are low.
Define gluconeogenesis
Formation of glucose from non-carbohydrate sources
Glycerol (from fat) and amino acids are converted to glucose
What is the metabolic process for excess glucose?
Glycogenesis - excess glucose is stored as glycogen
How and where is starch digested?
In the mouth by salivary amylase secreted by the salivary glands
How and where are carbohydrates digested?
Small intestine by pancreatic amylase secreted from the pancreas or brush border enzymes from the intestinal cells of the microvilli.
How and where are proteins digested?
In the stomach from pepsin secreted from stomach and in the small intestine from trypsin secreted from the pancreas
How and where are lipids and triglycerides digested?
In the small intestine from lipases secreted from the the pancreas
What does gastric juice consist of?
Mucus - lubricates and mixes food
HCl - lowers pH of stomach (acid)
Intrinsic factor - absorption of vitB12
Pepsinogen - converted into pepsin by HCl
Gastrin - regulates stomach secretion and motility (a hormone)
What is the mechanism of short term food intake regulation?
Neural signals from the GI tract,
blood levels of nutrients and
hormones
What is the mechanism of long term food intake regulation?
Leptin (hormone) produced by adipose tissue. Rising levels of it stimulate the satiety area of the hypothalamus and falling levels stimulate the hunger area.
Other factors: stress, body temp, psychological factors)
What is the absorptive (fed) state and how does it work?
It occurs during and immediately following a meal
Anabolism exceeds catabolism.
Glucose is the main energy source for cells (converted to ATP) or is stored as glycogen or fat.
Triglycerides are taken up by cells or stored as fat
Amino acids are synthesised to protein
Insulin controls the absorptive state and is stimulated by blood glucose and amino acid levels
What is the post absorptive (fasted) state and how does it work?
Occurs between meals
Catabolism exceeds anabolism
Fatty acids are main fuel source (remaining glucose is spared only for brain RBCs).
Glycogenesis and gluconeogenesis occur in liver to release glucose into blood and maintain blood glucose level.
Is regulated by glucagon and sympathetic activity
What is lipogenesis
Synthesis of triglycerides and lipids
What are the 3 main stage of ATP formation from glucose?
- Glycolysis: conversion of glucose molecule into 2 molecules of pyruvic acid
- Krebs (citric acid) cycle
- Electron transport chain
