UNIT 3.
DIGESTIVE AND
1.
DIGESTIVE SYSTEM
1) Which are the relationships between cellular respiration and the systems that perform nutrition in human body?
Digestive system processes food and
transforms them into nutrients that can be
distributed to all cells
Respiratory system: capture O2 from the air
and eliminate CO2 released during cellular
respiration
Excretory system: expels waste products that are released during cellular
metabolism.
Circulatory system: take the nutrients and O2 from the digestive and respiratory
system to the cells, and take their waste products and CO2 from cells to the
excretory and respiratory system, respectively.
1.
THE DIGESTIVE
SYSTEM
.2) What is the digestive system made up?
The digestive system is made up of the digestive tract and the accessory glands.
3) What is the digestive tract?
The digestive tract is a tube about 8 meters long. It starts in the mouth and
ends at the anus. It has the following parts: oral cavity, pharynx, oesophagus, stomach,
small intestine and large intestine.
4) What are the accessory glands?
The accessory glands are organs that secrete substances into a digestive tract. They
are the salivary glands, the gastric glands, and the intestinal glands (liver and
5) Sign the parts of the digestive system in a picture and translate them.
6) Name and explain the processes that happen before digestion.
They are insalivation, mastication and swallowing (insalivación, masticación y deglución).
7) Which are the functions of saliva?
It starts the digestion of starch (found in a lot of foods) thanks to amylase enzyme.
It destroys some bacteria in the food.
It helps the food to pass down towards the pharynx and oesophagus.
8) Name the salivary glands.
They are three pairs; parotid, sublingual, and submandibular.
9) Name the functions of the tongue.
Tongue makes mastication easier and helps to mix food and saliva. It has taste buds to
10) Name the types of teeth and each function. How many of each type of teeth has an adult human being?
8 Incisors (incisivos): cut food
4 Canines (caninos): tear food
8 Premolars and 12 molars (premolares y molars): grain and crush food
11) Name the involuntary and voluntary phases of swallowing.
Voluntary: when we push up our tongue against the palate
squeezing the food to the back of the oral cavity
Involuntary: they are reflex movements. The soft palate
close the nasal cavity, the larynx moves up and the
epiglottis close its upper openings, moving the bolus into the
throat. Other movements let the bolus to pass through the
oesophagus (peristalsis)
Activities: 3, 4, 5, 7, 8, 9, 10, 11, 13 and 14.
12) What is the pylorus? What is cardia?
The Pylorus is the output valve of the stomach. It’s usually closed.
The cardia is the entrance valve. It’s usually opened.
13) Explain the digestive process made in stomach.
The food bolus stay at stomach between 3 and 4 hours, where it mixes with gastric juice.
Gastric juice contains pepsin, that digests proteins, and hydrochloric acid, which
activates pepsin and destroys bacteria.
The result of it is the Chyme, more fluid than bolus. When the chyme is acid enough the
14) Which substances does gastric juice contain? How does it work?
Gastric juice contains pepsin and hydrochloric acid. The hydrochloric acid actives the
pepsin enzyme, and this digest proteins into amino acids that are absorbed.
15) Why the stomach walls are not damaged by gastric juice?
Because the stomach walls are protected by mucus.
16) Structure and function of small intestine.
The small intestine begins at the pylorus and finish at the ileocaecal valve. It has three
sections: Duodenum, jejunum and ileum (duodeno, yeyuno e íleon).
In the small intestine, the chime is going to be in contact with digestive juices secreted
by liver and pancreas (bile and pancreatic juice).
17) Which are two functions of liver?
It produces bile, that is released through the ampulla of Vater into the duodenum, and it
emulsify fats thanks to the bile salts (it lets fats to be solved in water), and it lets the
digestion of fats.
Besides, liver destroy any toxic molecule that enter the body.
18) How is the bile secretion?
Bile is not secreted directly. It is stored in gall gladder and is released only when
there is some food in the small intestine.
19) What is the function of bile?
Bile emulsifies fats that means, it lets the fats to be solved in water, and, in this manner
it can be digested.
20) Which is the function of pancreatic juice?
Pancreatic juice enters into duodenum through ampulla of Vater, and it contains digestive
enzymes (like trypsin, which breaks down proteins, and sodium bicarbonate, that neutralize
acid chyme.
21) Which substances does it contain?
25) Make a simple scheme about how digestion works.
26) Name the nutrients got in the digestion.
We get monosaccharides, as glucose or fructose, from more complex carbohydrates.
We get glycerol and fatty acids from fats.
We get amino acids from proteins.
27) How nutrients are absorbed?
Nutrients pass to the bloodstream through absorption. Absorption takes place through the
membrane of the small intestine cells.
To increase this surface, small intestine is covered in folds; the folds are formed by
finger-like structures called villi, which make the intestine surface 10 times bigger.
The cells in the surface of the villi are covered by microvilli that make the intestine
surface 70 times bigger. The overall score of all these structures is small intestine has a
surface of 330 m2, a bigger surface than a tennis court.
Down the intestine, the cells are absorbing the nutrients, and they pass to the capillary
there are inside the villi. Fats pass towards lymphatic capillary.
28) Structure and functions of the large intestine.
Large intestine begins in ileocaecal valve and finish in anus. Caecum, colon and rectum
(ciego, colon y recto).
Large intestine is the responsible of most of the water and mineral salts absorbed, and
there waste products are compacted to form faeces, and they are moved though some
29) What is gut flora? What are its functions?
Gut flora are the colonies of microorganisms which live in our digestive system, above all in
our colon. They help us in the absorption, and have a symbiotic relationship with us: we let
them to eat from our chyle and they release vit K and B12 which we absorb.
