The muscle are biological motors which convert chemical energy into force and mechanical work.
This biological machinery is composed of proteins – which is actomyosin and the fuel is ATP.
With the use of muscles we are able to act on our environment.
The muscle are biological motors which convert chemical energy into force and mechanical work.
This biological machinery is composed of proteins – which is actomyosin and the fuel is ATP.
With the use of muscles we are able to act on our environment.
THIS PRESENTATION INCLUDES DETAILED INFORMATION ABOUT ACCESSORY ORGANS OF DIGESTIVE SYSTEM..i,e TEETH, TONGUE, SALIVARY GLANDS, PANCREAS, LIVER AND GALL BLADDER
Human digestive system structure and function
overview
Major organs
Mouth
Esophagus
Stomach
small intestine
large intestine
Acessory organs:
Liver
gall bladder
Pancreas.
Human digestive system
Major organs
Mouth
Esophagus
Stomach
small intestine
large intestine.
Acessory organs:
Liver
Gall bladder
Pancreas.
MAJOR ORGANS The Mouth
pH: 7
The first part of the digestive system
the entry point of food.
Structures in the mouth that aids digestion
Teeth – cut, tear, crush and grind food.
Salivary glands – produce and secrete saliva into the oral cavity.
saliva
moistens the food
contains enzymes (ptyalin or salivary amylase)
begins digestion of starch into smaller polysaccharides.
Function:
Mechanical digestion.
increasing surface area for faster chemical digestion.
The Esophagus
a tube connecting the mouth to the stomach
running through the Thoracic cavity.
Location:
lies behind windpipe (Trachea).
The trachea has as an epiglottis
preventing food from entering the windpipe,
moving the food to the esophagus while swallowing.
Food travels down the esophagus, through a series of involuntary rhythmic contractions (wave-like) called peristalsis.
Function:
The lining of the esophagus secretes mucus
lubricating
to support the movement of food.
Esophageal sphincter:
bolus reaches the stomach
must pass through a muscular ringed valve called the esophageal sphincter (Cardiac Sphincter).
Function:
prevent stomach acids from back flowing into the esophagus.
Stomach
J-shaped muscular sac
Has inner folds (rugae)
Increasing surface area of the stomach.
Function:
Stomach performs mechanical digestion
HOW By churning the bolus and mixing it with the gastric juices
secreted by the lining of the stomach.
GASTRIC JUICES HCl, salts, enzymes, water and mucus)
HCL helps break down of food and kills bacteria that came along with the food.
The bolus is now called Chyme.
Enzymes in stomach:
Acidic environment
HCl secreation
kill any microbes that are found in the bolus,
creating a pH of 2.
Mucus prevents the stomach from digesting itself.
Pepsin secreation
responsible for initiating the breakdown of proteins (in )food.
hydrolyzes proteins to yield polypeptides.
pH is 2, the enzyme from the salivary glands stops breaking down carbohydrates.
Pyloric sphincter:
chyme moves from the stomach to the small intestine.
It passes through a muscular ringed sphincter called the pyloric sphincter.
stomach does not digest itself Why ?
Protective Mechanism:
three protective mechanisms.
First the stomach only secretes small amounts of gastric juices until food is present.
Second the secretion of mucus coats the lining of the stomach protecting it from the gastric juices.
The third mechanism is the digestive enzyme pepsin is secreted in an inactive protein c
The primitive blueprint for the heart and circulatory system emerged with the arrival of the third mesodermal germ layer in bilaterians. Since then, hearts in animals have evolved from a single layered tube to a multiple chambered heart in due course of time.
Why do animals need to breathe?
Breathing is important to organisms because cells require energy (oxygen) to move, reproduce and function. Breath also expels carbon dioxide, which is a by-product of cellular processes within the bodies of animals.
Respiration is the process of releasing energy from food and this takes place inside the cells of the body.
The process of respiration involves taking in oxygen (of air) into cells, using it for releasing energy by burning food, and then eliminating the waste products (carbon dioxide and water) from the body.
Respiration is essential for life because it provides energy for carrying out all the life processes which are necessary to keep the organisms alive.
The energy produced during respiration is stored in the form of ATP (Adenosine Tri- Phosphate) molecules in the cells of the body and used by the organism as when required.
KEY POINTS
Life started in an anaerobic environment in the so called ‘primodial broth’ (a mixture of organic molecules.
Subsequently, oxygen strangely enough became an crucial factor for aerobic metabolism especially in the higher life forms.
The rise of an oxygenic environment was an important event in the diversification of life.
It evoked a dramatic shift from inefficient to sophisticated oxygen dependent oxidizing ecosystems.
Anaerobic fermentation, the metabolic process that prevailed for the first about 2 billion years of the evolution of life, was a very inefficient way of extracting energy from organic molecules. Ex: A molecule of glucose, e.g., produces only two molecules of ATP (≈ 15 kCal) compared with 36 ATP molecules (≈ 263 kCal) in oxygenic respiration.
Aerobic metabolism must have developed at a critical point when the partial pressure of oxygen rose from an initial level to one adequately high to drive it passively across the cell membrane.
Respiration is a complex and highly integrated biomechanical, physiological, and behavioral processes.
The transfer of O2 occurs through a flow of tissue barriers and compartments by diffusion down a partial pressure gradient, which drops to about zero at the mitochondrial level.
Acquisition of molecular oxygen (O2) from the external fluid media (water and air) and the discharge of carbon dioxide (CO2) into the same milieu is the primary role of respiration.
The respiratory system is a biological system consisting of specific organs and structures.
The vertebrate brain
The vertebrate brain is the main part of the central nervous system. The brain and the spinal cord make up the central nervous system,
In most of the vertebrates the brain is at the front, in the head. It is protected by the skull and close to the main sense organs.
Brains are extremely complex and the part of human and animal body. The brain controls the other organs of the body, either by activating muscles or by causing secretion of chemicals such as hormones and neurotransmitters.
Muscular action allows rapid and coordinated responses to changes in the environment.
The brain of an adult human weights about 1300–1400 grams .
In vertebrates, the spinal cord by itself can cause reflex responses as well as simple movement such as swimming or walking. However, sophisticated control of behaviour requires a centralized brain.
The structure of all vertebrate brains is basically the same.
At the same time, during the course of evolution, the vertebrate brain has undergone changes, and become more effective.
In so-called 'lower' animals, most or all of the brain structure is inherited, and therefore their behaviour is mostly instinctive.
In mammals, and especially in man, the brain is developed further during life by learning. This has the benefit of helping them fit better into their environment. The capacity to learn is seen best in the cerebral cortex.
Three principles
The brain and nervous system is essentially a system which makes connections. It has input from sense organs and output to muscles. It is connected in several ways with the endocrine system, which makes hormones, and the digestive system and sex system. Hormones work slowly, so those changes are gradual.
The brain is a kind of department store. It has, all inter-connected, departments which do different things. They all help each other gather senses.
Much of what the body does is not conscious. Basically, much of the body runs on automatic (breathing, heart beat, hungry, hair growth) adjusted by the autonomic nervous system. The brain, too, does much of its work without a person noticing it. The unconscious mind refers to the brain activities which are hardly ever noticed.
Sense organs are the specialized organs composed of sensory neurons, which help us to perceive and respond to our surroundings. There are five sense organs – eyes, ears, nose, tongue, and skin.
External receptors (exteroceptors): sense organs for touch, smell, taste, sight and hearing.
Internal receptors (interocepyors): these sense organs found in the body which detect the temperature, pain, hunger, thirst, fatigue and muscle position.
The GI tract is a series of hollow organs joined in a long, twisting tube from the mouth to the anus. The hollow organs that make up the GI tract are the mouth, esophagus, stomach, small intestine, large intestine, and anus. The liver, pancreas, and gallbladder are the solid organs of the digestive system.
THIS PRESENTATION INCLUDES DETAILED INFORMATION ABOUT ACCESSORY ORGANS OF DIGESTIVE SYSTEM..i,e TEETH, TONGUE, SALIVARY GLANDS, PANCREAS, LIVER AND GALL BLADDER
Human digestive system structure and function
overview
Major organs
Mouth
Esophagus
Stomach
small intestine
large intestine
Acessory organs:
Liver
gall bladder
Pancreas.
Human digestive system
Major organs
Mouth
Esophagus
Stomach
small intestine
large intestine.
Acessory organs:
Liver
Gall bladder
Pancreas.
MAJOR ORGANS The Mouth
pH: 7
The first part of the digestive system
the entry point of food.
Structures in the mouth that aids digestion
Teeth – cut, tear, crush and grind food.
Salivary glands – produce and secrete saliva into the oral cavity.
saliva
moistens the food
contains enzymes (ptyalin or salivary amylase)
begins digestion of starch into smaller polysaccharides.
Function:
Mechanical digestion.
increasing surface area for faster chemical digestion.
The Esophagus
a tube connecting the mouth to the stomach
running through the Thoracic cavity.
Location:
lies behind windpipe (Trachea).
The trachea has as an epiglottis
preventing food from entering the windpipe,
moving the food to the esophagus while swallowing.
Food travels down the esophagus, through a series of involuntary rhythmic contractions (wave-like) called peristalsis.
Function:
The lining of the esophagus secretes mucus
lubricating
to support the movement of food.
Esophageal sphincter:
bolus reaches the stomach
must pass through a muscular ringed valve called the esophageal sphincter (Cardiac Sphincter).
Function:
prevent stomach acids from back flowing into the esophagus.
Stomach
J-shaped muscular sac
Has inner folds (rugae)
Increasing surface area of the stomach.
Function:
Stomach performs mechanical digestion
HOW By churning the bolus and mixing it with the gastric juices
secreted by the lining of the stomach.
GASTRIC JUICES HCl, salts, enzymes, water and mucus)
HCL helps break down of food and kills bacteria that came along with the food.
The bolus is now called Chyme.
Enzymes in stomach:
Acidic environment
HCl secreation
kill any microbes that are found in the bolus,
creating a pH of 2.
Mucus prevents the stomach from digesting itself.
Pepsin secreation
responsible for initiating the breakdown of proteins (in )food.
hydrolyzes proteins to yield polypeptides.
pH is 2, the enzyme from the salivary glands stops breaking down carbohydrates.
Pyloric sphincter:
chyme moves from the stomach to the small intestine.
It passes through a muscular ringed sphincter called the pyloric sphincter.
stomach does not digest itself Why ?
Protective Mechanism:
three protective mechanisms.
First the stomach only secretes small amounts of gastric juices until food is present.
Second the secretion of mucus coats the lining of the stomach protecting it from the gastric juices.
The third mechanism is the digestive enzyme pepsin is secreted in an inactive protein c
The primitive blueprint for the heart and circulatory system emerged with the arrival of the third mesodermal germ layer in bilaterians. Since then, hearts in animals have evolved from a single layered tube to a multiple chambered heart in due course of time.
Why do animals need to breathe?
Breathing is important to organisms because cells require energy (oxygen) to move, reproduce and function. Breath also expels carbon dioxide, which is a by-product of cellular processes within the bodies of animals.
Respiration is the process of releasing energy from food and this takes place inside the cells of the body.
The process of respiration involves taking in oxygen (of air) into cells, using it for releasing energy by burning food, and then eliminating the waste products (carbon dioxide and water) from the body.
Respiration is essential for life because it provides energy for carrying out all the life processes which are necessary to keep the organisms alive.
The energy produced during respiration is stored in the form of ATP (Adenosine Tri- Phosphate) molecules in the cells of the body and used by the organism as when required.
KEY POINTS
Life started in an anaerobic environment in the so called ‘primodial broth’ (a mixture of organic molecules.
Subsequently, oxygen strangely enough became an crucial factor for aerobic metabolism especially in the higher life forms.
The rise of an oxygenic environment was an important event in the diversification of life.
It evoked a dramatic shift from inefficient to sophisticated oxygen dependent oxidizing ecosystems.
Anaerobic fermentation, the metabolic process that prevailed for the first about 2 billion years of the evolution of life, was a very inefficient way of extracting energy from organic molecules. Ex: A molecule of glucose, e.g., produces only two molecules of ATP (≈ 15 kCal) compared with 36 ATP molecules (≈ 263 kCal) in oxygenic respiration.
Aerobic metabolism must have developed at a critical point when the partial pressure of oxygen rose from an initial level to one adequately high to drive it passively across the cell membrane.
Respiration is a complex and highly integrated biomechanical, physiological, and behavioral processes.
The transfer of O2 occurs through a flow of tissue barriers and compartments by diffusion down a partial pressure gradient, which drops to about zero at the mitochondrial level.
Acquisition of molecular oxygen (O2) from the external fluid media (water and air) and the discharge of carbon dioxide (CO2) into the same milieu is the primary role of respiration.
The respiratory system is a biological system consisting of specific organs and structures.
The vertebrate brain
The vertebrate brain is the main part of the central nervous system. The brain and the spinal cord make up the central nervous system,
In most of the vertebrates the brain is at the front, in the head. It is protected by the skull and close to the main sense organs.
Brains are extremely complex and the part of human and animal body. The brain controls the other organs of the body, either by activating muscles or by causing secretion of chemicals such as hormones and neurotransmitters.
Muscular action allows rapid and coordinated responses to changes in the environment.
The brain of an adult human weights about 1300–1400 grams .
In vertebrates, the spinal cord by itself can cause reflex responses as well as simple movement such as swimming or walking. However, sophisticated control of behaviour requires a centralized brain.
The structure of all vertebrate brains is basically the same.
At the same time, during the course of evolution, the vertebrate brain has undergone changes, and become more effective.
In so-called 'lower' animals, most or all of the brain structure is inherited, and therefore their behaviour is mostly instinctive.
In mammals, and especially in man, the brain is developed further during life by learning. This has the benefit of helping them fit better into their environment. The capacity to learn is seen best in the cerebral cortex.
Three principles
The brain and nervous system is essentially a system which makes connections. It has input from sense organs and output to muscles. It is connected in several ways with the endocrine system, which makes hormones, and the digestive system and sex system. Hormones work slowly, so those changes are gradual.
The brain is a kind of department store. It has, all inter-connected, departments which do different things. They all help each other gather senses.
Much of what the body does is not conscious. Basically, much of the body runs on automatic (breathing, heart beat, hungry, hair growth) adjusted by the autonomic nervous system. The brain, too, does much of its work without a person noticing it. The unconscious mind refers to the brain activities which are hardly ever noticed.
Sense organs are the specialized organs composed of sensory neurons, which help us to perceive and respond to our surroundings. There are five sense organs – eyes, ears, nose, tongue, and skin.
External receptors (exteroceptors): sense organs for touch, smell, taste, sight and hearing.
Internal receptors (interocepyors): these sense organs found in the body which detect the temperature, pain, hunger, thirst, fatigue and muscle position.
The GI tract is a series of hollow organs joined in a long, twisting tube from the mouth to the anus. The hollow organs that make up the GI tract are the mouth, esophagus, stomach, small intestine, large intestine, and anus. The liver, pancreas, and gallbladder are the solid organs of the digestive system.
753 Learning OutcomesAfter reading this chapter, .docxpoulterbarbara
75
3
Learning Outcomes
After reading this chapter, you will be able to:
3.1 Describe the processes and organs involved in
digestion.
3.2 Explain how food is propelled through the gas-
trointestinal tract.
3.3 Identify the role of enzymes and other secre-
tions in chemical digestion.
3.4 Describe how digested nutrients are absorbed.
3.5 Explain how hormones and the nervous sys-
tem regulate digestion.
3.6 Explain how absorbed nutrients are trans-
ported throughout the body.
3.7 Discuss the most common digestive disorders.
True or False?
1. Saliva can alter the taste of food. T/F
2. Without mucus, the stomach would digest itself. T/F
3. The major function of bile is to emulsify fats. T/F
4. Acid reflux is caused by gas in the stom-ach. T/F
5. The primary function of the large intes-tine is to absorb water. T/F
6. Feces contain a high amount of bacteria. T/F
7. The lymphatic system transports all nutrients through the body once they’ve been absorbed. T/F
8. Hormones play an important role in digestion. T/F
9. Diarrhea is always caused by bacterial infection. T/F
10. Irritable bowel syndrome is caused by an allergy to gluten. T/F
See page 110 for the answers.
Digestion,
Absorption,
and Transport
M03_BLAK8260_04_SE_C03.indd 75 12/1/17 11:28 PM
76 Chapter 3 | Digestion, Absorption, and Transport
The digestion of food begins even before you take that first bite. Just the sight and smell of homemade apple pie stimulates the release of saliva in
the mouth. The secretion of saliva and other digestive juices starts a cascade of
events that prepares the body for digestion, the chemical and mechanical
processes by which the body breaks food down into individual nutrient
molecules ready for absorption. Food components that aren’t absorbed are
excreted as waste (feces) by elimination. Although these are complex
processes, they go largely unnoticed. You consciously chew and swallow the
pie, but you don’t feel the release of chemicals or the muscular contractions
that cause it to be digested or the absorption of nutrient molecules through
the intestinal lining cells. In fact, you may be unaware of the entire process
until about 48 hours after eating, when the body is ready to eliminate waste.
In this chapter, we explore the processes of digestion, absorption, and
elimination, the organs involved, and the other biological mechanisms that
regulate our bodies’ processing of food and nutrients. We also discuss the causes
and treatments of some common gastrointestinal conditions and disorders.
What Are the Processes and Organs
Involved in Digestion?
LO 3.1 Describe the processes and organs involved in digestion.
Digestion, absorption, and elimination occur in the gastrointestinal (GI) tract, a mus-
cular tube approximately 20–24 feet long in an adult. Stretched vertically, the tube would
be about as high as a two-story building. It provides a barrier between the food within the
lumen (the hollow .
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Mechanical & Chemical Digestion
1.
2. Biology 30S Unit 2 DIGESTION & NUTRITION Chemical Digestion Recall, many organs of the digestive system secrete different substances. These secretions all play different roles in the chemical digestion of food. During the chemical digestion of food, enzymes break down large food molecules by the process of hydrolysis . During hydrolysis, a water molecule is added at the site where a bond is broken.
3. Biology 30S Unit 2 DIGESTION & NUTRITION Chemical Digestion - Mouth The mouth begins the process of carbohydrate digestion through the action of saliva. The enzyme found in saliva, salivary amylase , starts the chemical digestion of starch, converting it from a polysaccharide to the disaccharide maltose.
4.
5. Biology 30S Unit 2 DIGESTION & NUTRITION Chemical Digestion - Stomach A very important constituent of gastric juices is the substance pepsinogen . Pepsinogen is not an enzyme but a forerunner of the enzyme pepsin . The hydrochloric acid secreted increases the acidity of the stomach contents to a pH of 2 or lower. At this pH, pepsinogen is converted to pepsin, an active enzyme which begins the chemical digestion of proteins into peptides.
6. Biology 30S Unit 2 DIGESTION & NUTRITION Chemical Digestion - Stomach Salivary amylase functions best at pH 6 or 7 (very slightly acidic or neutral). Therefore, it becomes inactive when it reaches the stomach, and consequently, digestion of starch does not take place there. The mucous coats the cells lining the stomach and protects them from the digestive action of the enzyme pepsin.
7. Biology 30S Unit 2 DIGESTION & NUTRITION Chemical Digestion – Small Intestine Final digestion of proteins and carbohydrates must occur, and fats have not yet been digested. Villi have cells that produce intestinal enzymes which complete the digestion of peptides and sugars.
8. Biology 30S Unit 2 DIGESTION & NUTRITION Chemical Digestion – Small Intestine The upper part, the duodenum, is the most active in digestion. Secretions from the liver and pancreas are used for digestion in the duodenum. Epithelial cells of the duodenum secrete a watery mucous which acts to protect its lining from pepsin and HCl. The pancreas secretes digestive enzymes and stomach acid-neutralizing sodium bicarbonate . The sodium bicarbonate neutralizes the acidic chyme, allowing the enzymes in the small intestine to function and protecting the intestinal wall.
9. Biology 30S Unit 2 DIGESTION & NUTRITION Chemical Digestion – Small Intestine The liver produces bile , which is stored in the gall bladder before entering the bile duct into the duodenum. Bile contains cholesterol, phospholipids, bilirubin, and a mix of salts. Bile salts emulsify fats – breaking them down into progressively smaller fat globules until they can be acted upon by fat digesting enzymes. They also aid in neutralizing the chyme from the stomach.
10. Biology 30S Unit 2 DIGESTION & NUTRITION Chemical Digestion – Small Intestine The chemical digestion that begins in the small intestine is a result of pancreatic secretions. Starch and glycogen are broken down into maltose through the action of pancreatic amylase . Proteases continue the breakdown of protein that began in the stomach and form small peptide fragments and some amino acids. Lipases break down fats into fatty acids and glycerol.
11. Biology 30S Unit 2 DIGESTION & NUTRITION Chemical Digestion – Small Intestine Finally, the villi in the small intestine itself release enzymes which complete the digestive process. Maltase , lactase , and sucrase are three carbohydrate digesting enzymes which break down the maltose, sucrose and lactose into monosaccharides. Lactose intolerance results from a lack of the enzyme lactose. Peptidase breaks down peptides into amino acids and nuclease breaks down nucleic acids into sugars and nitrogen bases.
12.
13. Biology 30S Unit 2 DIGESTION & NUTRITION Sites of Chemical Digestion Starch Mouth and SI Protein Stomach and SI Fats SI
14. Biology 30S Unit 2 DIGESTION & NUTRITION Functions of Secretions Besides chemical digestion, certain secretions of our digestive system serve other functions. These functions include the ability to lubricate and the ability to protect our body.
15. Biology 30S Unit 2 DIGESTION & NUTRITION Functions of Secretions Lubrication – the mucus found throughout our digestive system (saliva, stomach, SI) plays a major role in lubricating food as it passes through the digestive system. What would happen to the process of digestion if your salivary glands stopped producing saliva?
16. Biology 30S Unit 2 DIGESTION & NUTRITION Functions of Secretions Protection – the mucus found throughout our digestive system (saliva, stomach, SI) plays a major role in protecting our body from the other digestive secretions of our digestive system. What would happen to the process of digestion if your stomach stopped producing mucus?
17.
18. Biology 30S Unit 2 DIGESTION & NUTRITION pH The pH of a solution can have several effects on the structure and activity of enzymes. Enzymes are affected by changes in pH. The most favorable pH value - the point where the enzyme is most active - is known as the optimum pH. Extremely high or low pH values generally result in complete loss of activity for most enzymes. pH is also a factor in the stability of enzymes.
20. Biology 30S Unit 2 DIGESTION & NUTRITION Temperature Like most chemical reactions, the rate of an enzyme-catalyzed reaction increases as the temperature is raised. The reaction rate increases with temperature to a maximum level, then abruptly declines with further increase of temperature.
22. Biology 30S Unit 2 DIGESTION & NUTRITION Inhibitors Enzyme inhibitors are substances which alter the catalytic action of the enzyme and consequently slow down, or in some cases, stop catalysis. There are three common types of enzyme inhibition - competitive, non-competitive and substrate inhibition.
23. Biology 30S Unit 2 DIGESTION & NUTRITION Control of Digestive Secretions A fascinating feature of the digestive system is that it contains its own regulators, both hormonal and nervous. The major hormones that control the functions of the digestive system are produced and released by cells in the lining of the stomach and small intestine. These hormones are released into the blood of the digestive tract, travel back to the heart and through the arteries, and return to the digestive system, where they stimulate digestive juices and cause organ movement.
27. Biology 30S Unit 2 DIGESTION & NUTRITION Nervous Control of Digestive Secretions Two types of nerves help to control the action of the digestive system, Extrinsic and Intrinsic. Extrinsic (outside) nerves come to the digestive organs from the subconscious part of the brain or from the spinal cord. Intrinsic (inside) nerves, which make up a very dense network embedded in the walls of the esophagus, stomach, small intestine, and colon.
28. Biology 30S Unit 2 DIGESTION & NUTRITION Extrinsic Nerves These nerves release a chemical called acetylcholine and another called adrenaline. Acetylcholine causes the muscle of the digestive organs to squeeze with more force and increase the "push" of food and juice through the digestive tract. Acetylcholine also causes the stomach and pancreas to produce more digestive juice. Adrenaline relaxes the muscle of the stomach and intestine and decreases the flow of blood to these organs. Seeing, smelling or tasting food produces gastric secretions even before there is food in the stomach.
29. Biology 30S Unit 2 DIGESTION & NUTRITION Intrinsic Nerves The intrinsic nerves are triggered to act when the walls of the hollow organs are stretched by food. They release many different substances that speed up or delay the movement of food and the production of juices by the digestive organs.
30. Biology 30S Unit 2 DIGESTION & NUTRITION Absorption Absorption is a very important part of the digestive process. It allows digested food to be transferred to the bloodstream and transported to the cells in the body. Most absorption occurs in the duodenum and jejunum of the small intestine. However, some water, certain ions, and such drugs as aspirin and ethanol are absorbed from the stomach and large intestine into the blood.
31. Biology 30S Unit 2 DIGESTION & NUTRITION Absorption in Small Intestine The villi of the small intestine greatly increase the surface area for absorption. Villi increase the surface area by a factor of 10. The epithelial cells that cover the villi are lined with microvilli that further increase the surface area. Absorption through the intestinal wall takes place by diffusion and active transport. Many substances must move through the membranes from an area of low concentration to one of higher concentration. Amino acids, for example, are absorbed by active transport.
32. Biology 30S Unit 2 DIGESTION & NUTRITION Absorption in Small Intestine A thin-walled capillary (small blood vessel) network extends through the core of the villus (singular form of villi). Most dissolved nutrients, which have already been absorbed by passive transport through the epithelial cells, pass into the capillaries. However, the products of fat digestion do not pass into the capillaries, but instead enter a vessel called a lacteal , which is part of the lymphatic system of the body. The absorbed fat droplets are transported to adipose (fat) tissue where they are stored.
33.
34. Biology 30S Unit 2 DIGESTION & NUTRITION Reconstruct a flowchart adding as much information as you can regarding digestion, enzymes, absorption, etc.. Mouth/ Throat Esoph- agus Stomach Small Intestine Large Intestine Rectum/ Anus
![Biology 30S Unit 2 DIGESTION & NUTRITION ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]](https://image.slidesharecdn.com/mechanicalchemicaldigestion-101007131352-phpapp02/85/Mechanical-Chemical-Digestion-1-320.jpg)
