UNIT 5: Systems involved in nutrition I: Digestive and respiratory systems

1-Systems involved in nutrition

There are four systems involved in nutrition:

-Digestive system: Transforms food into nutrients which can be used by our cells.

-Respiratory system: Captures oxygen and eliminates carbon dioxide and water produced by cell respiration.

-Circulatory system: Transports substances (nutrients and waste products) through the body.

-Excretory system: Cleans the blood eliminating waste products produced by cell metabolism.

2- Digestive system structure

The Mouth has different parts:

-Teeth:

-Tongue: has taste buds.

-Salivary glands: Parotids, submandibular and sublingual glands. They produce saliva.

The epiglottis is a flap at the entrance of the pharinx which closes when we swallow and forces food to go down the esophagus instead of the respiratory system.

3- How does the digestive system work?

We can be observed five steps in the digestive systems:

1-Ingestion:Food enters the gastrointestinal tract through the mouth. In the mouth two things occur:

-Physical (mechanical) digestion: teeth and tongue are involved in breaking apart food.

-Chemical digestion: In the mouth, salivary glands produce saliva which contains the enzyme amylase which acts on starch, breaking it into maltose.

2-Swallowing (deglutition): After swallowing, the bolus(ball of food made by the actions of the teeth, tongue, and saliva) moves to the stomach through the esophagus which uses waves in its wall called pesristaltic movementsto move the bolus.

3-Digestion:

Digestion in the stomach:

-Physical: the stomach is a muscular storage organ that churns the food.

-Chemical: gastric juice, produces by gastric glands, mixes with bolus. Gastric juice contains:

a) Pepsin: enzyme that breaks down protein.

b) HCl: hydrochloric acid. It allows pepsin to work.

c) Mucus: protectsthe stomach from HCl damage.

The stomach contents arenow called chyme.

Digestion in the intestines:

Gland involved / Juice involved / Nutrient / Final product
Salivary gland (mouth) / Saliva (amylase) / Carbohydrates (starch) / Glucose
Gastric glands (Stomach) / Gastric juice (pepsin) / Proteins / Amino acids
Intestinal glands
(duodenum) / Intestinal juice / Carbohydrate
Proteins / Glucose
Amino acids
Pancreas / Pancreatic juice
(Duodenum) / Carbohydrate
Proteins
Lipids / Glucose
Amino acids
Small lipids
Liver / (bile) Gallbladder
(Duodenum) / Lipids / Small lipids

*The table shows digestion in the intestines and in the rest of the digestive system.

4-Absorption:

Absorption is the transport of nutrients from the intestines to the blood. Most of nutrients are absorbed in jejunum and illeum. Water and mineral salts are absorbed in the colon.The intestinal wall is covered by villi (folds formed by cells with microvilli in their surface) which increase the absorption surface. Inside the villi there are blood capillaries which pick up nutrients to be carried through the body.

5-Egestion:

Egestion is the discharge of undigested food (as feces) from the digestive tract via the anus.

Feces are formed when food is transformed by bacteria in the large intestine.

3- Digestive system disorders

  • Cavities: When we eat or drink something that contains sugar, the bacteria uses it to produce acids. These acids destroy tooth's emanel and dentine, making small holes in them. You should brush your teeth after eating and go to the dentist regularly.
  • Constipation: Whenan individual has hard feces that are difficult to expel. It occurs when the colon has absorbed too much water from the food that is in the colon. To avoid constipation we should consume foods rich in fiber, drink a lot of water and do exercise.
  • Ulcers: Are painful sores that can be found in the stomach lining or small intestine. Stomach ulcers are caused by excess acid. Treatment will vary depending on the cause of your ulcer. Most ulcers can be treated with:

- Acid blockers

- In serious cases, surgery may be required.

  • Gastroenteritis: is inflammation of the gastrointestinal tract caused by viral or bacterial infections. It provokes symptoms likediarrhea, vomiting, and abdominal pain. The primary treatment for gastroenteritis is rehydration (by drinking rehydration solution to recover water and mineral salts lost) and then to go on a bland diet.
  • Hepatic cirrhosis: is the severe damage of the liver caused by long-term exposure to toxins such as alcohol or viral infections.

4-Respiratory system

-Function:

Is to take in oxygen from atmoshere (which is be used by cell respiration) and release carbon dioxide and water (produced in that process).

-Structure:


-Breathing process:

Inhalation exhalation

Diaphragm: Contracts andRelaxes and

curves down curves up

Intercostal muscles: Contract Relaxe

AirEnters the body Moves out

-Gas exchange:

Gaseous exchange occur in alveoulus by diffusion.This alveolus is surrounded by blood capilaries. In diffusion,oxygen which is more in concentration inalveolus and low in blood, go to the blood from alveolus and carbon dioxide which is more in concentration inpulmonary capillary and low in alveolus go to the alveolus from pulmonary capillary blood.

-Respiratory disorders:

  • Bronchitis is an inflammation or swelling of the bronchi. There are two types:

-Acute bronchitis: Due to viral infections (like flu).

-Chronic bronchitis: Due to toxic substances in smokers.

  • Asthma is the inflammation and narrowing of the bronchial tubes.
  • A cold is a bacterial or viral infection. Some symptoms are: runny nose, coughing, sneezing, headache, temperature.
  • Tuberculosis is a bacterial infection that destroys the lung tissue.