Unit 4 - Anatomy Flashcards
What are the four major functions of the human digestive system?
ingestion: the taking in of nutrients
digestion: the physical and chemical breakdown of complex food molecules into smaller molecules
absorption: the transfer of digested nutrients from the digestive system to the bloodstream
egestion: the removal of waste food materials from the body
What are the two types of digestion?
1) Mechanical: breaks substances down physically into smaller pieces
2) Chemical: the breakdown of substances by enzymes and acids into their components
What does the mouth do in digestion?
mechanical and chemical breakdown
Explain the teeth and their role in digestion
Location: mouth
Digestion: mechanical
incisors (8): cutting and biting
canines (4): ripping and tearing
molars (20): grinding (8 premolars, 8molars, 4 wisdom teeth/third molars)
Explain the tongue and its role in digestion
Location: mouth
Digestion: mechanical
-a muscle (one of the strongest in the body)
-helps with chewing, speech, and swallowing
-taste → taste buds have nerve endings which send a message to your brain
Explain the salivary glands and their role in digestion
Location: mouth
Digestion: mechanical and chemical
parotid, submaxillary, sublingual
-contains enzymes that increase the rate of chemical reactions, water, and mucous
-contains the enzyme amylase that begins the breakdown of starch
-saliva also moistens the food (mechanical)
Explain the pharynx and its role in digestion
Digestion: mechanical
a muscular tube that helps food along
Explain the epiglottis and its role in digestion
Digestion: no digestion
-a flap of cartilage that covers your trachea when you swallow to prevent choking
Explain the esophagus and its role in digestion
Digestion: mechanical
-muscular tube connecting the pharynx to the stomach
-peristalsis (wave-like muscle contractions) facilitates the movement of food down this tube
Explain the stomach and its role in digestion
Digestion: mechanical and chemical
-the gastroesophageal sphincter prevents food and acid from moving up the esophagus
-special cells secrete hydrochloric acid and enzymes
-it is lined with special mucus-secreting cells, which prevents the stomach from “eating” itself with its own acid
-The stomach is made of smooth muscle which contracts and mixes the food until it’s in a semi-liquid state called chyme.
-The pyloric sphincter prevents food from leaving the stomach prematurely and controls the entry into the small intestine.
-proteins are partly digested in the stomach and continue digestion in the small intestine, lipids and carbohydrates are not digested in the stomach
What are the four layers of the stomach?
mucosa: innermost layer, extensively
folded, secretes gastric juice (mixture
of digestive enzymes, acid and mucus),
its epithelial cells divide rapidly to heal
any damage
submucosa: the layer of connective tissue that contains networks of nerves and blood vessels, these nerves detect when food is present and initiate the release of a hormone called gastrin (stimulates the release of gastric juice)
muscularis or muscle layers: consists of smooth muscles that contract frequently, churning and mixing the
food with gastric juices to produce chyme
serosa: smooth, outermost layer
that holds the stomach in place and
secretes a lubricating fluid that
eliminates friction between organs
What do gastric juices in the stomach do?
gastric juice kills many harmful microorganisms that are ingested with the food, stops the action of amylase, but provides the necessary pH for the activation of other digestive enzymes, such as pepsinogen
the hydrochloric acid present in the gastric juice converts pepsinogen to its active form, pepsin, which begins the breakdown of proteins into separate amino acids
Explain the liver and its role in digestion
Digestion: mechanical
-it produces bile which is a highly basic substance that helps neutralize the chyme from the stomach
-bile also acts as an emulsifier (the body’s detergent), which helps it break down fat into smaller droplets so that digestive enzymes can act on this nutrient more efficiently
Besides producing bile, what else does the liver do?
-it regulates the level of glucose in the bloodstream
-it converts excess glucose into glycogen or fat
-it removes ammonia (NH3) and turns it into urea, which is mixed with water to form urine
-produces cholesterol and blood clotting agents
Explain the gall bladder and its role in digestion
Digestion: no digestion
-stores bile that is made in the liver
-drips bile into duodenum as food passes by
-helps to deodorize the stool (reduces the action of bacteria)
Explain the pancreas and its role in digestion
Digestion: chemical
-produces bicarbonates which function as antacids and help control the pH of the duodenum
-produces many digestive enzymes
-produces hormones such as insulin
Explain the small intestine and its role in digestion
Digestion: chemical
-7 meters long
-it completes the process of chemical digestion
-contains finger-like projections called villi that are responsible for absorbing nutrients into the bloodstream
-the villi hang from the wall of the small intestine and cover its entire surface
-peristalsis moves material through the small intestines
What two characteristics make the small intestine ideal for absorbing nutrients?
The characteristics of the small intestine that make it ideal for absorbing nutrients:
A) length – because it is long, the nutrients have time to be absorbed
B) the walls of the small intestine have tremendous surface area due to:
the lining has folds: increase surface area by 3X
folds are covered in tiny villi: increase surface area by 10X
microvilli on the surface of the villi: increase surface area by 20X
What are the three sections of the small intestine?
the duodenum, the jejunum, the ileum
What happens when absorption occurs within the small intestine?
-monosaccharides (product of carbohydrate digestion), amino acids (product of protein digestion), and water-soluble minerals are absorbed into a network of capillaries that carry these nutrients from the vilus to an artery for transport through the circulatory system
-glycerol and fatty acids (products of lipid digestion) and fat-soluble minerals are absorbed into a lacteal that carries these nutrients through the lymphatic system
-most of the absorption of nutrients has occurred by the time the food reaches the jejunum
Explain the large intestine and its role in digestion
Digestion: no digestion
-a one-way valve called the ileo-caecal sphincter prevents food from moving backwards into the small intestine
-fibre enters the large intestine along with waste
-peristalsis moves the waste into the rectum and then the anus where it is eliminated
-main function is to absorb water*
What is the air we breathe?
The air we breathe is a mixture of different gases: 78% nitrogen, 21% oxygen, 1% argon, 0.04% carbon dioxide, and lesser amounts of other gases.
What process allows oxygen to obtain energy from food?
aerobic cellular respiration
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy
(glucose + oxygen → carbon dioxide + water + energy)
Where does gas exchange in humans and other mammals occur?
the lungs and the body cells.
Explain the nasal passages and their function in the respiratory tract
NASAL PASSAGES: (filter, warm, and humidify)
-narrow and winding with many grooves
-coarse hairs filter out dust particles and
pathogens
-blood vessels help to warm the air
-mucous helps to moisten the air
-particles are swept to the mouth (and then swallowed) by the beating cilia
Explain the trachea and its function in the respiratory tract
-rigid with rings of cartilage that prevent
it from collapsing
-is lined with cilia, which move mucous
and debris up and away from the lungs
-divides into two bronchi which divide
further into smaller-diameter bronchioles
-the amount of cartilage decreases and smooth muscle increases as the tube diameter decreases
Explain the lungs and their function in the respiratory tract
-humans have two lungs (the right lung has 3 lobes, left lung has 2 lobes)
-the heart, large blood vessels, and the
esophagus is found between the lungs
-a membrane called the pleura covers the outer surface of the lungs and is lubricated by a thin film of liquid
-pleurisy is the inflammation of the pleura
What is pneumothorax?
A pneumothorax occurs
when air leaks into the space
between your lung and chest
wall (pleura). This air pushes
on the outside of your lung
and makes it collapse.
What does the lung tissue consist of?
-lung tissue is not dense but is much like a sponge that contains alveoli
-alveoli are tiny, hollow, elastic sacs (think a cluster of grapes)
-the walls of the alveoli are only one cell thick and lined with capillaries (tiny blood vessels – one cell thick) that allow gas to be exchanged between the
lungs and the blood
-there are approximately 100 000 000 alveoli per lung
-alveoli greatly increase the surface area of the lung tissue
Explain the alveoli and their site of gas exchange
OXYGEN (O2)
–moves from the lung tissue to the blood
CARBON DIOXIDE (CO2)
–moves from the blood to the lung tissue
→ gases move by the process of diffusion
Explain the control of breathing
Breathing is involuntary.
-It is controlled by the nervous system and the circulatory system
-We can temporarily, consciously control our breathing (holding our breath, talking, singing).
What is the medulla oblongata?
a part of the brain that monitors the amount of CO2 in the blood (through the
pH of the blood)
How does the medulla oblongata operate?
-An increase in aerobic cellular respiration increases the amount of carbon dioxide in the blood, which in turn produces carbonic acid and lowers the pH of the blood.
-Receptors in the medulla oblongata detect the lower pH and send nerve signals to the diaphragm and external intercostal muscles to initiate faster/more forceful movement.
What is our rate of breathing determined by?
the demand for oxygen or the need to eliminate CO2
-the O2 and CO2 levels in the blood are constantly monitored by chemical receptors in the brain, in the arteries leading to the brain, and the arteries leaving the heart
Describe and explain the breathing in movements and what occurs in the body
Inhalation/Inspiration (breathing in)
1) Rib muscles (external intercostals)
contract, moving the ribs up and
out; diaphragm contracts and
flattens.
2)The volume of the lungs increases.
3)Pressure in the lungs decreases.
4) Air rushes into the lungs to
equalize pressure.
Describe and explain the breathing out movements and what occurs in the body
Exhalation/Expiration (breathing out)
1) Rib muscles (external intercostals)
relax, moving ribs down and in;
diaphragm relaxes and becomes
dome-shaped (moves upwards).
2) Volume of lungs decreases.
3) Pressure in the lungs increases.
4) Air rushes out of the lungs to equalize
the pressure.
What is the diaphragm?
-muscle located below the lungs that creates more space in lung cavity to flatten and fill with air, or relax and allow air out
-facilitates movement of air in and out of the body
Explain gas exchange and transportation of oxygen in the respiratory tract
-Oxygen is not very soluble in blood
but some does dissolve in the plasma.
-Hemoglobin (Hgb), found in the red
blood cells greatly increases the
carrying capacity of the blood
*hemoglobin contains 4 iron (Fe) atoms
*iron provides the binding sites for O2
*280 million hemoglobin molecules per red blood cells
-Hemoglobin is more attracted to CO
(carbon monoxide) than O2, thus if both
are present in inhaled air, hemoglobin
will fill its sites with CO first
-Carbon monoxide can be found in car
exhaust and cigarette smoke (a product
of incomplete combustion).
Explain gas exchange and transportation of carbon dioxide in the respiratory tract
Carbon dioxide is 20X more soluble in blood than O2.
→ In the blood:
-9% transport as CO2
-27% combine with hemoglobin
-64% combine with water in plasma to form carbonic acid (H2CO3)
