A Level Biology- The effects of CF on the airways and other body systems, Topic 2

Why can't CF lungs regulate water in mucus? [full explanation]

1- The CFTR gene codes for the CFTR protein, which is a chloride ion channel (facilitated diffusion) 2- With CF, the gene is mutated and the CFTR protein has the wrong shape 3- So, the channel does not allow movement of chloride ions into the mucus 4- The solute concentration in the mucus decreases 5- Therefore water doesn't move into the mucus from the tissue fluid by osmosis 6- This results in the mucus becoming viscous/thick/sticky

What is the difference between exocrine and endocrine glands?

Exocrine glands have ducts, which they secrete substances into. Endocrine glands are ductless and secrete hormones directly into the blood.

How is food chemically broken down in the gut?

Glands secrete digestive enzymes into the lumen of the gut, where they act as catalysts to speed up the extracellular breakdown of food molecules.

How does the pancreas help in the chemical breakdown of food?

Groups of pancreatic cells produce enzymes that catalyse the breakdown of proteins, carbs, and lipids. These digestive enzymes are delivered to the gut in pancreatic juice, released through the pancreatic duct. (The pancreas is also an endocrine gland releasing hormones such as insulin into the blood)

How do sweat glands help regulate body temperature?

In an individual without CF, CFTR and ENaC proteins allow reabsorption of sodium chloride from the sweat as it moves up the duct towards the skin surface. The sweat that is released onto the skin and evaporates is therefore hypotonic.

Where does most chemical breakdown of food occur?

Most chemical breakdown of food molecules and the absorption of the soluble products of digestion occurs in the small intestine.

The cells that line the airways produce mucus. Why does the water content of this mucus need to be regulated?

Mucus water content is regulated to maintain a constant viscosity, because mucus must be runny enough to be moved by the beating cilia, but not so runny that the fluid floods the airway.

How does CF affect sweat?

Salt is normally reabsorbed from sweat using the CFTR channel. Since this does not function/is non existent with CF, the salt is not absorbed, making saltier sweat.

How is the pancreas affected by CF?

The pancreatic duct becomes blocked by sticky mucus, impairing the release of digestive enzymes. The lower concentration of enzymes within the small intestine reduces the rate of digestion. Food is not fully digested, so not all the nutrients can be absorbed. As a consequence, the faeces contain a higher proportion of partially digested and undigested food, so energy is lost. This is called malabsorption syndrome.

How is the water content of mucus regulated?

The regulation of the water content of mucus is achieved by the transport of sodium ions and chloride ions across the epithelial cells. Water then follows the ions by osmosis.

What are the additional complications due to the blocking of the pancreatic duct?

When pancreatic enzymes become trapped behind the mucus blocking the pancreatic duct, they damage the pancreas itself. The cysts of hard, damaged, or fibrosed tissue within the pancreas give the CF condition its name. Another complication occurs if damage occurs to cells within the pancreas that produce the hormone insulin, which is involved in the control of blood sugar levels. A form of diabetes can result.

How does CF affect the reproductive system?

-Females have a reduced chance of getting pregnant: a mucus plug develops in the cervix, stopping sperm from reaching the ovum. -Males often lack the vas deferens (sperm duct): this stops sperm leaving the testes, and if it is even present, it can be blocked by sticky mucus.

Where are the enzymes used for the chemical breakdown of food made?

A wide range of enzymes are produced by exocrine glands outside the gut (e.g. salivary glands, liver) and the pancreas. Enzymes are also built into the membranes of the gut epithelium.

What do sweat glands do?

Sweat glands are exocrine glands that initially secrete into their lumen a solution of salt and water that is isotonic to the blood.

Why do CF sufferers have difficulty maintaining body mass?

They have problems with digestion and absorption of nutrients. They also have high basal metabolic rates, and tend to have poor appetites.

What does a CF sufferer have to do to ensure they obtain sufficient nutrients and energy?

They require 120-140% of the recommended daily energy intake, and need to eat high-energy food to obtain sufficient nutrients and energy. They may also take food supplements containing digestive enzymes to help break down large food molecules.

Is the pancreas an endocrine or exocrine gland?

Trick question, it's both. It secretes insulin straight into the blood and digestive enzymes into a duct.