M10

(based on feedforward)

The enzymes salivary amylase, pancreatic amylase, maltase, sucrase and lactase work on the macronutrient __

carbohydrates

Carboxypeptidase and peptidase are enzymes that work on proteins. What are the other (3) enzymes that also works on this macronutrient?

pepsin, trypsin, chymotrypsin

The main enzymes that work on lipids are: (3)

lingual lipase, gastric lipase, pancreatic lipase

Pancreatic nucleases and nucleosidases are enzymes that work on:

nucleic acids 

What is a substrate?

The molecule that enzymes binds to and changes to create a chemical reaction

Enzymes that work on carbohydrates bind to substrates such as __ and __.

starch, disaccharides 

What does enzymes break bigger molecules of carbohydrates into? (3)

glucose, fructose, galactose

Enzymes bind to substrates such as __ and __ to break protein substances into __

proteins, peptides, amino acids

Enzymes that work on lipids bind to __ to produce products such as __ and __

triglycerids, monoglycerids and fatty acids

Within the mouth, saliva is produced from salivary glands like __ (3), which each has specific types of secretions (list each)

• parotid (serous)

• sublingual (mucous)

• submandibular (serous + mucous)

Saliva contains salivary __, which breaks down starch (a __) into __ (a disaccharide) - this is an __ mechanism

• amylase

• polysaccharide

• maltose

• extrinsic

The glands on the tongue contains the enzyme __ and starts the chemical digestion of lipids/fats into __

lingual lipase, fatty acids and glycerol 

Hydrochloric acid (HCl) is highly acidic and denatures proteins. It also activates __ (inactive) into __(an active enzyme)

pepsinogen, pepsin

Pepsin is a type of enzyme in the stomach that breaks down __ into __

proteins, peptides

Most of the digestion occurs in the duodenum of small intestine. The pancreas produces __ to aid the duodenum in further digestion.

pancreatic enzymes

Pancreatic amylase is a pancreatic enzyme that further breaks down __ into __

polysaccharides, disaccharides

Pancreatic lipase is a pancreatic enzyme that further breaks down __ into __

triglycerides, fatty acids + monoglycerides

Other than pancreatic amylase and lipase, pancreatic enzymes also includes __ (peptides → __) and __ (DNA/RNA → __)

• protease; amino acids

• nuclease; nucleotides

The liver produces bile which is concentrated and released into the duodenum by the gallbladder. Bile works on __ (enzyme) to assist in increasing SA by __ fats 

pancreatic lipase; emulsifying 

Brush border enzymes are located on the __ of jejenum and ileum, but mostly duodenum. These enzymes, __ (5), completes digestion for absorption (the final stage)

• microvilli

• maltase, sucrase, lipase, peptidase, nucleosidase

Maltase, sucrase and lactase are all enzymes that work on carbohydrates, how do they differ?

• maltase: maltose → glucose

• sucrase: sucrose → glucose + fructose

• lactase: lactose → glucose + galactose

The brush border enzymes, peptidases and nucleosidases, what do they break peptides and nucleotides into?

• peptides → amino acids 

• nucleotides → nitrogenous bases + sugars + phosphates 

How is mechanical digestion occurring in the mouth?

teeth and tongue breaks the food to form a bolus

Chemical digestion in the mouth mainly occurs by the salivary amylase in saliva starting carbohydrate digestion. What is the composition of saliva? Include percentages and solutes.

• 99.5% → water

• 0.5% → electrolytes, salivary amylase, IgA, mucous, lysozymes)

What are the functions of saliva?

• moistens food

• buffers pH (neutralises acids)

• lubricates bolus

• begins starch digestion

• protects mucosa (mouth’s tissue)

The stomach’s mucosa (innermost layer) is lined with __ cells (__ epithelium), and contains gastric pits with specialised cells. These cells include: (4)

• surface mucous, simple columnar

• mucous neck, parietal, chief, enteroendocrine cells

Mucous neck cells in the gastric pit secretes __

mucus

Parietal cells in the gastric pit secretes __ and __

HCl and intrinsic factor

Chief cells in the gastric pit secretes __, which is what HCl acts on

pepsinogen

Enteroendocrine cells in the gastric pit includes G-cells, __ and __. Respectively, they secrete __, histamine and __

• enterochromaffin-like cells, somatostatin-containing cells

• gastrin, somatostatin

What is the difference between enterochromaffin and somatostatin cells?

enterochromaffin: secretes histamine to stimulate HCl secretions in parietal cells, increasing acidity 

somatostatin: secretes somatostatin to inhibit gastrin, decreasing acidity

What is the function of gastrin?

signals parietal cells to produce HCl 

The stomach’s mechanic role is to mix broken-down food with __ to produce __ - this is a process called __. The muscle externa enables this churning movement, what are its three layers?

• gastric juice, chyme, churning

• oblique, circular, longitudinal

Is there any absorption role in the stomach?

A little, only reabsorbs alcohol and some drugs.

Villi increases surface area in the duodenum for digestion and absorption. They are covered in specialised epithelial cells called __. These cells have microvilli and form the __. Among these cells, there are __ cells, which secretes __ to lubricate and protect the intestinal wall from ____ and acids.

• enterocytes, brush border

• goblet, mucus, digestive enzymes

What is the function of the intestinal/tubular glands at the base of villi in the duodenum mucosa?

secretes intestinal juice and can produce new epithelial cells

The submucosa contains mostly blood vessels, lymph and nerves. What is the specialised gland in the submucosa of duodenum?

Brunner’s glands → secretes alkaline mucus to neutralise the acidic chyme from stomach

What is contained within intestinal juice/ succus entericus? 

water, mucus, bicarbonate and final-stage enzymes (maltase, sucrase, lactase, peptidases and nucleosidases) 

what are the two main components of exocrine function?

1. acinar cells: produces pancreatic enzymes

2. dust cells: secretes bicarbonate ions into pancreatic juice to neutralise acidity

The liver is made of lobules with __ surrounding a central vein. The functions include (3)

hepatocytes

• produces bile

• stores glycogen and vitamins

• detoxifies blood via hepatic portal circulation

Differentiate the hormones that control production and secretion of bile 

1. secretin - stimulates liver to produce more bile 

2. cholecystokinin (CCK) - stimulates release of bile into duodenum. 

The large intestines contain pouches called __ which allows mechanical digestion. These pouches produce slow __ contractions to do what? (2)

• haustra, haustral

• mix contents to absorb water and move faeces towards rectum

What does the large intestine have instead of digestive enzymes to maintain chemical digestion? What is its main function? (2)

bacterial flora → ferments remaining carbs into gas and synthesises vitamins K and B 

What are the last substances that are reabsorbed in the large intestine? (3)

water (forms solid faeces), electrolytes, vitamins

Monosaccharides (glucose, galactose, fructose) are small enough to be absorbed by the intestinal cells. Glucose and __ enters the cell via active co-transport with __. __ enters via __ diffusion. All monosaccharides moves out of epithelial cell and into bloodstream via __ diffusion.

galactose, sodium (Na+), fructose, facilitated, facilitated

What is the pathway of monosaccharides (carbohydrates) absorption after passing through the intestinal epithelium?

enter capillaries → hepatic portal vein → liver

Amino acids are absorbed into the epithelial cells by active transport, using __ or __ ions as __. They move out of the cell and into the capillaries by simple __

Na+, H+, symporters, diffusion

The process of lipid absorption goes as follows:

1. __ (enzyme) breaks fats/__ into fatty acids (FFAs) and __ (MGs)

2. __ + FFAs and MGs to form __, which creates a __ border and __ centre. 

3. Micelles attach to the PM of enterocyte, where __ and __ leaves and diffuses across PM

4. Inside the cell, FFAs and MGs combine together again to form __

5. Triglycerides combine with __ and cholesterol to form __

6. These are too large to diffuse across blood capillaries, therefore they diffuse into __ via exocytosis

7. This substances moves as lymph and empties into the bloodstream at the __ duct

1. pancreatic lipase; triglycerides; monoglycerids

2. bile salts; micelles; hydrophilic; hydrophobic

3. FFAs and MGs

4. triglycerides

5. proteins; chylomicrons

6. lacteals

7. thoracic

Absorption of vitamins:

• __ vitamins (A, D, E & K) are absorbed with __

• __ vitamins (B, C & __) are absorbed by __

• Vitamin B12 combines with __ factor and transports into cells

• fat-soluble; lipids

• water-soluble; biotin; diffusion

• intrinsic

Absorption of electrolytes

1. Na+ and K+ → __ diffusion

2. Cl-, idodide, nitrate → __ across electrical potential

3. iron, magnesium, phosphate → __ transport

1. facilitated

2. passively

3. active

How is water absorbed?

by osmosis 

Intrinsic control of the digestion regulation involves the enteric NS. The __ plexus is located between __ and induces __ contractions. The __ plexus is located in the __ and controls __ and __ to the gut wall. 

• myenteric; muscle layers; muscle 

• submucosal; submucosa; secretions and BF 

Extrinsic control of digestion regulation involves the brain and spinal cord. Differentiate between the parasympathetic and sympathetic divisions (nerves and its response)

• para - vagus nerve; stimulates digestion (increases mechanisms in intrinsic control)

• symp - spinal nerves; inhibits digestion (decreases intrinsic mechanisms)

The endocrine control of digestion regulation involves three main hormones. __ is triggered when __ enters the stomach, stimulating the release of __ and __ secretion. __ is triggered when __ chyme enters the duodenum, __ is released to neutralise this acidity. CCK (__) is released when __ chyme enters the duodenum, stimulating the release of __ enzymes.

1. gastrin; food; HCl and enzyme

2. secretin; acidic; bicarbonate ions

3. cholecystokinin; fatty, protein-rich; pancreatic

The cephalic phase occurs before food enters the stomach. The __(4) of food stimulates the brain to send signals via the __ nerve to the stomach. This causes gastric glands to stimulate the release of __(3), and the hormones __ (from G-cells) and __ (from enterochromaffin-like cells) 

• sight, smell, taste or thought 

• vagus 

• HCL, pepsin and mucus 

• gastrin and histamine 

When food enters the stomach, the gastric phase occurs. The __ of stomach sends APs to the __ via the vagus nerve. This stimulates the release of __ secretions and __ reflexes. Gastrin arrive with histamine from the bloodstream and increases __ (parietal cells) and __ (chief cells) secretions and increases __

• stretch; medulla oblongata

• stomach; enteric

• HCl and pepsinogen; motility

The intestinal phase is triggered when chyme in the duodenum has a pH less than __ or contains __. In response, the __ reflex __ gastric secretion, which includes:

1. duodenum __receptors signalling the medulla to decrease __ signals = decreases __ and __

2. __ NS = __ secretions and __ in the stomach 

3. with an __ in secretin and CCK, __ acid and __ secretion is decreased  

• 2; lipids 

• enterogastric; inhibits 

• 1. chemo; motor; HCl and pepsin 

• 2. enteric; decreases; movement 

• 3. increase; stomach; enzyme 

What reflex controls GIT activity within the mouth?

mastication reflex

What reflex controls GIT activity within the pharynx/oesophagus?

swallowing reflex 

What are the reflexes within the stomach that controls GIT activity?

• cephalic, gastric and intestinal phases

• enterogastric reflex

What reflex in the small intestine controls GIT activity? What are its responses?

• gastroileal reflex

• increases ileal peristalsis and relaxes ileocecal sphincter

What are the three reflexes within the large intestine (colon) to control GIT activity?

gastrocolic, duodenocolic, defecation

What is the difference between gastrocolic, duodenocolic and defecation reflexes within the large intestine?

• gastrocolic: stimulates peristalsis in colon after eating

• duodenocolic: moves faeces through the colon

• defecation: expels faeces from the rectum