digestive system

Question 1

what are the functions of the digestive system?

Answer 1

1. Ingestion: Taking in food and water through the mouth.
2. Digestion: Breaking down food (complex) into smaller molecules through mechanical and chemical processes.
3. Absorption: Taking in nutrients, water, and electrolytes from the digested food into the bloodstream through the walls of the small intestine.
4. Elimination: Removing undigested waste products from the body as feces through the large intestine and rectum.

Question 2

what is the gastrointestinal (GI) tract? what are its organs?

Answer 2

the tube-like passageway that runs from the mouth to the anus. It’s where food travels as it’s digested, absorbed, and eventually eliminated from the body.

Organs of the GI Tract:
Mouth
Pharynx
Esophagus
Stomach
Small intestine
Large intestine (colon)
Rectum
Anus
(accessory glands)

Question 3

what are the accessory glands of the digestive system?

Answer 3

While the gastrointestinal (GI) tract is the main pathway for food, several other organs play crucial roles in digestion. These are called accessory organs. They don’t directly process food but produce substances essential for digestion.

*Salivary glands: Produce saliva, which contains enzymes to break down carbohydrates and moisten food for swallowing.
*Liver: Produces bile, which helps in the digestion of fats.
*Gallbladder: Stores and concentrates bile produced by the liver.
*Pancreas: Produces digestive enzymes that break down carbohydrates, proteins, and fats

Question 4

what are the tunics of the gastrointestinal (GI) tract?

Answer 4

The wall of the gastrointestinal (GI) tract is composed of four layers, also known as tunics.

1. Mucosa- The innermost layer.
   Composed of three sublayers:
   Epithelium: The lining of the GI tract, specialized for different functions (absorption, secretion, protection).
   Lamina propria: Loose connective tissue containing blood vessels, nerves, and lymphatic tissue.
   Muscularis mucosae: A thin layer of smooth muscle that creates folds in the mucosa, increasing surface area.
2. Submucosa- Connective tissue layer containing blood vessels, nerves, and lymphatic vessels. Houses the submucosal plexus (Meissner’s plexus), a network of nerves controlling secretions.
3. Muscularis Externa (Muscularis Propria) - Responsible for the movement of food through the GI tract.
   Composed of two layers of smooth muscle:
   Inner circular layer: Contracts to decrease the diameter of the GI tract. Outer longitudinal layer: Contracts to shorten the GI tract.
   Contains the myenteric plexus (Auerbach’s plexus), a network of nerves controlling motility.
4. Serosa or Adventitia - The outermost layer.
   Serosa: Covers organs within the peritoneal cavity.
   Adventitia: Connective tissue covering organs outside the peritoneal cavity.

Question 5

define peritoneum

Answer 5

The peritoneum is a thin, transparent membrane that lines the inside of the abdomen and covers most of the abdominal organs.
Parietal peritoneum: Lines the inner wall of the abdomen.
Visceral peritoneum: Covers the abdominal organs

Question 6

what are the salivary glands?

Answer 6

Salivary GlandsSalivary glands are exocrine glands that produce saliva, which they secrete into the oral cavity through a system of ducts.
Parotid glands: Located in front of the ears.
Submandibular glands: Located under the lower jaw.
Sublingual glands: Located under the tongue.

Question 7

define saliva, its composition, its functions

Answer 7

Saliva is a clear, slightly alkaline fluid produced by the salivary glands in the mouth.

Composition of Saliva:
Water
Electrolytes (sodium, potassium, calcium, bicarbonate)
Mucus
Enzymes (amylase for carbohydrate digestion)
Immunoglobulins (antibodies)

Functions of Saliva:
Digestion: Saliva contains enzymes, such as salivary amylase, that begin the breakdown of carbohydrates.
Lubrication: Moistens the mouth, making it easier to chew, swallow, and speak.
Protection: Contains antibodies and antimicrobial substances that help fight bacteria and prevent infections.
Cleaning: Helps to wash away food particles and debris, reducing the risk of tooth decay.
Taste: Dissolves food particles, allowing taste buds to detect flavors.
pH balance: Helps maintain a neutral pH in the mouth, protecting tooth enamel.

Question 8

define salivary amylase

Answer 8

Salivary amylase, also known as ptyalin, is an enzyme found in saliva that initiates the breakdown of starch into simpler sugars. This is the first step in the digestive process of carbohydrates.

Question 9

define lysozyme

Answer 9

Lysozyme is an enzyme that acts as a natural antibacterial agent. It’s found in various bodily fluids and tissues, including tears, saliva and mucus.

Question 10

what are the 3 parts of the pharynx?

Answer 10

Nasopharynx: Located behind the nasal cavity, it is primarily involved in respiration.

Oropharynx: Situated behind the oral cavity, it serves as a passageway for both air and food.

Laryngopharynx: The lowest part of the pharynx, connects to both the esophagus (for food) and the larynx (for air).

Question 11

describe the esophagus

Answer 11

The esophagus is a muscular tube that connects the pharynx (throat) to the stomach.

*Muscular tube: Composed of both smooth and skeletal muscles.
*Peristalsis: The esophagus uses rhythmic contractions (peristalsis) to push food down towards the stomach.
*Sphincters: It’s equipped with two sphincters:
Upper esophageal sphincter (UES): Prevents air from entering the esophagus.
Lower esophageal sphincter (LES): Prevents stomach contents from flowing back into the esophagus (acid reflux).
*Length: Approximately 25 centimeters (10 inches) long.

Question 12

does digestion take place in the esophagus?

Answer 12

NO!!
The esophagus is primarily a muscular tube that transports food from the mouth to the stomach.

Question 13

what are the phases of swallowing?

Answer 13

1. Voluntary phase: Under conscious control. Food is chewed and mixed with saliva to form a bolus. The tongue propels the bolus towards the back of the mouth.
2. Pharyngeal Phase - Involuntary phase: Begins as the bolus reaches the back of the mouth. The soft palate elevates to prevent food from entering the nasal cavity. The epiglottis closes to prevent food from entering the trachea. The upper esophageal sphincter relaxes to allow the bolus to enter the esophagus.
3. Esophageal Phase - Involuntary phase: Peristaltic contractions move the bolus through the esophagus to the stomach. The lower esophageal sphincter relaxes to allow the bolus to enter the stomach.

Question 14

is the movement in the esophagus due to gravity?

Answer 14

No, the movement of food through the esophagus is primarily due to peristalsis, not gravity.

Question 15

define peristalsis

Answer 15

Peristalsis is a series of wave-like muscle contractions that move food through the digestive tract. It begins in the esophagus and continues through the stomach, small intestine, and large intestine. it’s the involuntary muscular action that pushes food along the digestive system.

Question 16

what’s the antrum?

Answer 16

This is the lower part of the stomach, shaped like a funnel. It’s where food is mixed with digestive juices before it’s passed into the small intestine.

Question 17

what’s the pylorus?

Answer 17

The pylorus is the lower, narrow opening of the stomach that connects to the small intestine. It acts as a valve, controlling the passage of food from the stomach into the duodenum (the first part of the small intestine).

Question 17

define gastric pits

Answer 17

Gastric pits are small depressions or indentations found in the lining of the stomach. They are the openings to tubular structures called gastric glands. gastric pits are crucial for the production and release of the substances necessary for digestion.

Question 18

what are rugae in the stomach?

Answer 18

Rugae are prominent folds or ridges in the lining of the stomach. They are formed by the mucosa and submucosa layers. They allow the stomach to expand significantly when filled with food, increasing its capacity.

Question 19

what are the types of cells in the stomach?

Answer 19

1. Surface Mucous Cells:
   Located at the opening of the gastric pits.
   Secrete mucus to protect the stomach lining from the acidic environment.
2. Parietal Cells:
   Secrete hydrochloric acid (HCl) and intrinsic factor. HCl is essential for activating enzymes and killing bacteria, while intrinsic factors are necessary for vitamin B12 absorption.

3.Chief Cells:
Secrete pepsinogen (the inactive form of pepsin) an enzyme precursor that is activated by HCl to digest proteins.
Also secrete gastric lipase, an enzyme involved in fat digestion.

4. Endocrine Cells (G cells):
   Secrete hormones like gastrin in response to stimulation by the nervous system (gastrin stimulates parietal cells to secrete acids).

Question 20

define chyme

Answer 20

Chyme is a thick, semi-fluid mass of partially digested food that is expelled by the stomach into the duodenum (the first part of the small intestine).
It’s formed through the mechanical and chemical breakdown of food in the stomach, where it’s mixed with gastric juices containing enzymes and hydrochloric acid.

Question 21

what’s the pH of the stomach? why?

Answer 21

The pH of the stomach typically ranges from 1 to 3. This extremely acidic environment is crucial for several reasons:
*Activation of enzymes: The low pH is essential for activating digestive enzymes like pepsin, which breaks down proteins.
*Killing bacteria: The acidic environment helps to kill harmful bacteria that may be present in food.
*Denaturing proteins: The strong acid helps to unfold protein molecules, making them more accessible for digestion.

The primary source of this acidity is hydrochloric acid (HCl) secreted by parietal cells in the stomach lining.

Question 22

define intrinsic factors

Answer 22

Intrinsic factor is a glycoprotein produced by parietal cells in the stomach lining. It plays a crucial role in the absorption of vitamin B12 in the small intestine.

Question 23

what’s B12?

Answer 23

Vitamin B12, also known as cobalamin, is an essential nutrient that the body needs but cannot produce on its own. It’s found naturally in animal products like meat, fish, poultry, eggs, and dairy.

Red blood cell formation: Essential for the production of red blood cells, which carry oxygen throughout the body.
Nervous system health: Helps maintain the health of nerve cells and prevents nerve damage.
DNA synthesis: Involved in the creation of new DNA.

Question 24

what is saving the stomach from being destroyed by the high acidity?

Answer 24

The stomach lining produces a thick layer of mucus that acts as a barrier, protecting the cells from direct contact with the acidic gastric juices. Bicarbonate ions help to neutralize some of the acids in the mucus layer, providing additional protection.

Question 25

define gastrin

Answer 25

Gastrin is a hormone produced by G cells in the stomach and small intestine. Stimulates the release of gastric acid - this acid helps break down food and kill bacteria.

Question 26

explain the stomach secretion regulation

Answer 26

1. Cephalic Phase: This phase is initiated by the sight, smell, taste, or even thought of food (all stimulates centers in the medulla oblongata). The nervous system, primarily the vagus nerve stimulates the gastric glands to increase their secretory activity.
2. Gastric Phase: Once food enters the stomach, it triggers the release of gastrin, a hormone that further stimulates acid secretion. The presence of food also causes local reflexes that enhance secretion.
3. Intestinal Phase: As chyme enters the small intestine, hormones like secretin, and cholecystokinin (CCK) are released. secretin and CCK eventually inhibit gastric acid secretion, protecting the intestinal mucosa from excessive acidity.

(( Vagus nerve: This nerve stimulates the release of acetylcholine, which directly stimulates parietal cells to secrete hydrochloric acid. It also stimulates G cells to release gastrin.
Gastrin: Released by G cells in response to food, especially proteins. It stimulates parietal cells to secrete hydrochloric acid and chief cells to secrete pepsinogen.))

Question 27

what kind of digestion takes place in the stomach?

Answer 27

The stomach is where both mechanical and chemical digestion occur.

Question 28

what kind of digestion takes place in the mouth?

Answer 28

both mechanical and chemical digestion begin.

Question 29

what are the parts of the small intestine? (and sizes)

Answer 29

Duodenum:
Approximately 25 centimeters long. The shortest but widest part of the small intestine. Receives chyme from the stomach and bile from the liver and gallbladder, as well as enzymes from the pancreas.

Jejunum:
Approximately 2.5 meters long. The middle section of the small intestine. Most of the nutrient absorption occurs here.

Ileum:
Approximately 3 meters long. The longest and final section of the small intestine. Continues the absorption process, primarily absorbing vitamin B12 and bile acids.

Question 30

what ducts are empty to the small intestine?

Answer 30

1. Common Bile Duct - carries bile from the liver and gallbladder into the duodenum. Bile helps in the emulsification of fats, preparing them for digestion by enzymes.
2. Pancreatic Duct -Carries pancreatic juice into the duodenum.
   Pancreatic juice contains enzymes for digesting carbohydrates, proteins, and fats, as well as bicarbonate ions to neutralize stomach acid.

Question 31

what modifications are increasing the surface of the intestine and why?

Answer 31

The small intestine has undergone several structural adaptations to maximize its surface area for efficient nutrient absorption.

likeCircular Folds, Villi, Microvilli.

Question 32

define brush border

Answer 32

A brush border is a microscopic structure composed of densely packed microvilli that project from the surface of certain epithelial cells. It resembles a brush, hence the name.

Question 33

define enterocytes

Answer 33

Enterocytes are specialized epithelial cells that line the inner surface of the small intestine. They are primarily responsible for the absorption of nutrients from digested food.

*Nutrient absorption: They absorb carbohydrates, proteins, fats, vitamins, minerals, and water from the intestinal lumen into the bloodstream and lymphatic system.
*Digestion: Enterocytes contain enzymes in their brush border that complete the final stages of digestion.
*Barrier function: They form a protective barrier between the intestinal lumen and the underlying tissues.

Question 34

what’s the composition of the epithelium of the small intestine?

Answer 34

The epithelium of the small intestine is a simple columnar epithelium.

Key cell types within the epithelium:
*Enterocytes: These are the most abundant cells and are primarily responsible for nutrient absorption. They have microvilli on their apical surface, forming the brush border.
*Goblet cells: These cells secrete mucus, which lubricates the intestinal lining and protects it from digestive enzymes.
*Endocrine cells: These cells secrete hormones that regulate digestion, such as gastrin, secretin, and cholecystokinin.
*Crypts of Lieberkühn: Found at the base of the intestinal glands and secrete antimicrobial substances.
*Granular cells - protect from bacteria.

Question 35

what is the hepatic portal circulation?

Answer 35

The hepatic portal circulation is a unique blood circulatory system that carries blood from the gastrointestinal tract, spleen, pancreas, and gallbladder to the liver. Unlike most veins that carry blood directly to the heart, the hepatic portal vein carries blood to the liver for processing.
Nutrient processing: The liver processes nutrients absorbed from the intestines, such as glucose, amino acids, and fatty acids.
Detoxification: The liver removes toxins and harmful substances from the blood before it circulates to the rest of the body.

Question 36

what is the gallbladder?

Answer 36

The gallbladder is a small organ located just below the liver. Its primary function is to store and concentrate bile, a fluid produced by the liver that helps in the digestion of fats.

Question 37

define bile and its functions

Answer 37

Bile is a yellowish-green fluid produced by the liver, stored in the gallbladder, and released into the small intestine to aid in digestion.

functions of bile:
*Emulsification of fats: Bile breaks down large fat globules into smaller droplets, increasing their surface area for digestion by enzymes.
*Absorption of fats: Bile helps in the absorption of fatty acids and fat-soluble vitamins (A, D, E, and K) in the small intestine.
*Waste elimination: Bile also helps in the elimination of waste products, such as bilirubin, a breakdown product of hemoglobin.

Question 38

describe the liver and its functions

Answer 38

The liver is the largest solid organ in the human body and performs a multitude of crucial functions. Located in the upper right abdomen.

Functions of the Liver:
*Detoxification: The liver filters blood, removing harmful substances such as alcohol, drugs, and toxins.
*Metabolism: It processes nutrients from food, including carbohydrates, proteins, and fats, converting them into energy or storing them for later use.
*Bile production: The liver produces bile, a fluid essential for fat digestion and absorption.
*Protein synthesis: It produces many proteins essential for blood clotting, immune function, and other bodily processes.
*Storage: The liver stores vital substances like glucose (as glycogen), vitamins (A, D, E, K), and minerals (iron and copper).
*Blood filtration: It removes old red blood cells and processes bilirubin, a byproduct of red blood cell breakdown.
*Immune function: The liver plays a role in immune function by removing bacteria and filtering out foreign substances.

Question 39

is the pancreas endocrine or exocrine?

Answer 39

The pancreas is both endocrine and exocrine.

Exocrine function: The pancreas produces digestive enzymes that are released into the small intestine through ducts. These enzymes help in breaking down carbohydrates, proteins, and fats.
Endocrine function: The pancreas produces hormones, such as insulin and glucagon, which regulate blood sugar levels. These hormones are released directly into the bloodstream.

Question 40

define islets of Langerhans

Answer 40

Islets of Langerhans are clusters of cells within the pancreas that serve as the endocrine portion of the organ. These tiny structures are responsible for producing and releasing hormones directly into the bloodstream.

*Alpha cells: Produce glucagon, a hormone that raises blood sugar levels by stimulating the liver to release glucose.
*Beta cells: Produce insulin, a hormone that lowers blood sugar levels by promoting glucose uptake by cells.

Question 41

define insulin

Answer 41

Insulin is a hormone produced by the beta cells of the pancreas.

Functions of Insulin:
**Lowering blood sugar: Insulin helps glucose (sugar) from food get into the body’s cells to be used for energy.
**Storing glucose: Insulin promotes the storage of excess glucose in the liver and muscles as glycogen.
**Promoting fat storage: Insulin helps convert excess glucose into fat for storage.
**Facilitating protein synthesis: Insulin supports the building of proteins.

Question 42

define glucagon

Answer 42

Glucagon is a hormone produced by the alpha cells of the pancreas. Its primary function is to raise blood sugar levels.

When blood sugar levels drop too low (hypoglycemia), glucagon stimulates the liver to convert stored glycogen into glucose and release it into the bloodstream. It also promotes the breakdown of fats and proteins into glucose.

Question 43

what is the function of bicarbonate ions in the digestive system?

Answer 43

Bicarbonate ions play a crucial role in neutralizing the acidic chyme that enters the small intestine from the stomach. bicarbonate ions act as a buffer, maintaining the appropriate pH level for digestion to occur efficiently.

Neutralization: The highly acidic chyme is neutralized by bicarbonate ions, creating a slightly alkaline environment. This is essential for the optimal function of digestive enzymes in the small intestine.
Protection: By neutralizing the acid, bicarbonate ions help protect the lining of the small intestine from damage.

Question 44

what are proteolytic enzymes?

Answer 44

Proteolytic enzymes, also known as proteases or peptidases, are enzymes that break down proteins into smaller peptides or amino acids.

Question 45

define secretin (and functions)

Answer 45

Secretin is a hormone produced by the S cells in the lining of the duodenum, the first part of the small intestine. It is released in response to the acidic chyme entering the small intestine from the stomach.

Functions of Secretin:
*Stimulates pancreatic bicarbonate secretion: Secretin triggers the pancreas to release bicarbonate-rich fluid, which neutralizes the acidic chyme.
*Inhibits gastric acid secretion: Secretin helps to reduce the acidity of the stomach contents.
*Stimulates bile production: It increases the production of bile by the liver.

Question 46

define CCK (and functions)

Answer 46

Cholecystokinin (CCK) is a hormone produced by the small intestine in response to the presence of food, particularly fats and proteins.

Functions of CCK:
*Stimulates gallbladder contraction: CCK triggers the gallbladder to contract, releasing bile into the small intestine to aid in fat digestion.
*Stimulates pancreatic enzyme secretion: It prompts the pancreas to release digestive enzymes, including lipase for fat breakdown, protease for protein digestion, and amylase for carbohydrate digestion.
*Inhibits gastric emptying: CCK slows down the emptying of the stomach, allowing for proper digestion in the small intestine.
*Appetite regulation: CCK is believed to play a role in satiety (feeling full).

Question 47

define sphincter of Oddi

Answer 47

The sphincter of Oddi is a muscular valve located at the lower end of the common bile duct and pancreatic duct. It controls the flow of bile from the gallbladder and pancreatic juices from the pancreas into the small intestine (specifically, the duodenum).

Question 48

define colon (size + functions)

Answer 48

The colon is the largest part (1.5 meters) of the large intestine. It’s a long, tube-like organ that extends from the cecum to the rectum. Goblet cells are present throughout the colon and are responsible for producing and secreting mucus, which plays a crucial role in protecting the colon’s lining and facilitating the smooth passage of waste material.

Functions of the Colon:
*Water absorption: The primary function of the colon is to absorb water from the undigested food material.
*Electrolyte absorption: It also absorbs essential electrolytes like sodium and potassium.
*Waste processing: The colon processes waste products and forms solid stool.
*Bacterial fermentation: The colon houses beneficial bacteria that help in the fermentation of undigested material, producing vitamins like vitamin K and biotin.

Question 49

what’s the size of the cecum? what’s they size of the appendix?

Answer 49

Cecum - Typically 5 to 7 centimeters
Appendix - Averages around 9 centimeters

Question 50

what are the 2 kinds of digestion?

Answer 50

Mechanical Digestion: This involves the physical breakdown of food into smaller pieces. chewing, churning in the stomach, and the muscular contractions that move food through the digestive tract.

Chemical Digestion: This involves the use of enzymes to break down complex food molecules (the covalent bonds) into simpler ones that the body can absorb. This process occurs throughout the digestive system, starting in the mouth with saliva and continuing through the stomach and small intestine.

Question 50

How much time does it take for materials to go through the large intestine? and in the small intestine?

Answer 50

large -18-24
small - 3-5

Question 51

define crypst (colon)

Answer 51

A colon crypt is a tube-like gland found in the lining of the colon and rectum. They contain goblet cells.

It serves two primary functions:
Renewal of the intestinal lining: Colon crypt cells constantly divide and replace the old cells, ensuring the integrity of the intestinal wall.
Mucus production: These cells also produce mucus, which helps protect the colon lining and aids in the smooth passage of waste.

Question 52

define cotransporters

Answer 52

Cotransporters are specialized proteins embedded in cell membranes that facilitate the simultaneous transport of multiple substances across the membrane. They harness the energy from the movement of one substance (usually moving down its concentration gradient) to drive the movement of another substance against its concentration gradient.

Symporters: Transport two substances in the same direction.
Antiporters: Transport two substances in opposite directions.

Question 53

what are the 2 kinds of active transport?

Answer 53

Primary Active Transport:
Directly uses energy from ATP (Adenosine Triphosphate) to move substances across the cell membrane.

Secondary Active Transport:
Indirectly uses energy by coupling the movement of one substance down its concentration gradient (which releases energy) to drive the movement of another substance against its concentration gradient.

Question 54

define elimination

Answer 54

Elimination in the context of digestion refers to the final stage of the digestive process. It involves the removal of undigested food matter and waste products from the body. This process is also known as defecation.

Question 55

can cellulose be ingested?

Answer 55

humans cannot digest cellulose. We lack the necessary enzyme, cellulase, to break down its complex structure.

Question 56

define fibers

Answer 56

A type of carbohydrate that the human body cannot digest. It’s found abundantly in plant-based foods such as fruits, vegetables, whole grains, and legumes.
Fiber absorbs water, making stool softer and bulkier. This helps prevent constipation and promotes regular bowel movements.
Fiber slows down the digestion process, preventing spikes in blood sugar levels.

Question 57

describe the digestion of carbohydrates

Answer 57

The goal is to break down complex carbohydrates into simple sugars (glucose, fructose, and galactose) for absorption into the bloodstream.

Mouth:
Mechanical Digestion: Chewing breaks down food into smaller particles, increasing the surface area for enzyme action.
Chemical Digestion: Saliva contains salivary amylase, an enzyme that begins the breakdown of complex carbohydrates (starch) into simpler sugars (maltose).

2. Stomach:
   Carbohydrate digestion is minimal in the stomach due to the acidic environment that inactivates salivary amylase.
3. Small Intestine:
   Pancreatic Amylase: The pancreas releases pancreatic amylase into the small intestine, continuing the breakdown of complex carbohydrates into maltose and other disaccharides.
   Disaccharide Breakdown: Enzymes present in the small intestine, such as maltase, sucrase, and lactase, break down disaccharides (maltose, sucrose, lactose) into monosaccharides (glucose, fructose, and galactose).
4. Absorption:
   Monosaccharides are absorbed through the intestinal wall (enterocytes) into the bloodstream.
5. Transportation:
   Glucose is the primary energy source for cells. The liver plays a key role in regulating blood glucose levels.

Question 58

describe the absorption of different (carbohydrates (Fructose, Glucose and Galactose)

Answer 58

These simple sugars are transported across the intestinal wall into the intestinal cells (enterocytes). This process involves specific carrier proteins embedded in the cell membrane.
*Glucose and galactose are absorbed through a sodium-dependent active transport mechanism. This means they require energy to move against their concentration gradient.
*Fructose is absorbed through facilitated diffusion, which doesn’t require energy but still needs a carrier protein.

Question 59

define GLUT 2

Answer 59

It’s a type of glucose transporter protein found in the epithelial cells of the small intestine.
GLUT2 facilitates the transport of glucose from the intestinal cells (the cytosol of the enterocytes) into the bloodstream.

Question 60

define SGLT1

Answer 60

SGLT1 is a protein that transports both sodium (Na+) and glucose into cells simultaneously. It’s a type of cotransporter, meaning it carries multiple substances across the cell membrane at the same time. It is an active transporter. It uses the energy from the sodium gradient to move glucose against its concentration gradient.

Question 61

define GLUT 5

Answer 61

GLUT5 is a specific protein that facilitates the transport of fructose across cell membranes.
facilitates the transport of fructose from the lumen of the small intestine to the intestinal cells (the cytosol of the enterocytes) and than into the bloodstream.

Question 62

do the monosaccharides in the blood goes directly to the heart (and rest of the body) after absorption in the intestine?

Answer 62

No!
The blood, now enriched with monosaccharides, is transported via the hepatic portal vein to the liver. he liver plays a crucial role in processing these sugars. Fructose and galactose are often converted to glucose. The liver also regulates blood glucose levels by storing excess glucose as glycogen or releasing it into the bloodstream as needed. After processing in the liver, the blood containing glucose is released into the systemic circulation.

Question 63

define GLUT 4

Answer 63

GLUT4 is a glucose transporter protein that plays a crucial role in glucose uptake into cells, particularly in response to insulin.
It’s a facilitated diffusion.

Question 64

define emulsification

Answer 64

Emulsification is a crucial process in the digestion of fats. It involves breaking down large fat globules into smaller droplets, increasing their surface area. This makes it easier for digestive enzymes to interact with and break down the fats.

When fats enter the small intestine, bile is released into the duodenum. Bile salts, components of bile, act as emulsifiers, breaking down fat globules into smaller droplets.

Question 65

describe the digestion of lipids

Answer 65

Mouth:
Lingual lipase, an enzyme in saliva, begins the breakdown of triglycerides into fatty acids and diglycerides. However, this process is limited.

Stomach:
Gastric lipase continues the breakdown of triglycerides, but the acidic environment of the stomach limits its activity. Mechanical digestion through churning helps to break down food particles, including fats.

Small Intestine:
This is where most lipid digestion occurs.
Emulsification: Bile acids, produced by the liver and stored in the gallbladder, emulsify fats into smaller droplets, increasing their surface area.
Enzymatic digestion: Pancreatic lipase, an enzyme secreted by the pancreas, breaks down triglycerides into fatty acids and monoglycerides.
Further breakdown: Other enzymes like cholesterol esterase and phospholipase break down cholesterol esters and phospholipids.

Absorption:
Fatty acids, monoglycerides, cholesterol, and fat-soluble vitamins form micelles with bile salts.
Micelles transport these substances to the intestinal mucosa. Inside the intestinal cells, fatty acids and monoglycerides are re-esterified to form triglycerides, cholesterol esters, and phospholipids.
These lipids combine with proteins to form chylomicrons, which are transported through the lymphatic system to the bloodstream.

Question 66

describe the absorption of lipids

Answer 66

1. Micelle Formation: Bile salts form micelles, which are tiny spherical structures that surround and solubilize lipid digestion products.
2. Diffusion into Enterocytes: Micelles transport lipids to the brush border of the intestinal epithelial cells (enterocytes). The lipid components diffuse (simple diffusion) from the micelles into the enterocytes.
3. Re-esterification: Inside the enterocytes, fatty acids and monoglycerides are recombined by the rER to form triglycerides. Cholesterol and phospholipids are also re-synthesized.
4. Chylomicron Formation: The newly formed lipids combine with cholesterol, phospholipids, and proteins to create chylomicrons.
5. Exocytosis and Lymphatic System: Chylomicrons are too large to enter the bloodstream directly, so they are released into the lymphatic system via exocytosis.
6. Entry into Bloodstream: The lymphatic system eventually merges with the bloodstream, allowing chylomicrons to enter the circulation.

Question 67

define micelles

Answer 67

A micelle is a tiny spherical particle formed by molecules called surfactants. These molecules have a unique structure with one end that is attracted to water (hydrophilic) and another end that is repelled by water (hydrophobic).

Question 68

define chylomicrons

Answer 68

Chylomicrons are large lipoprotein particles that transport dietary lipids (fats) from the intestines to other parts of the body. They are composed primarily of triglycerides, but also contain cholesterol, phospholipids, and proteins.

Question 69

define chyle

Answer 69

Chyle is a milky-white fluid formed in the small intestine during the digestion of fatty foods. It’s essentially lymph that is rich in emulsified fats or free fatty acids.
Chyle is transported through the lymphatic system, eventually entering the bloodstream via the thoracic duct.

Question 70

what are the differences between LDL and HDL?

Answer 70

LDL (Low-Density Lipoprotein)
Often referred to as “bad” cholesterol.
Transports cholesterol from the liver to cells throughout the body.
Excess LDL can build up in artery walls, forming plaque and increasing the risk of heart disease and stroke.

HDL (High-Density Lipoprotein)
Often referred to as “good” cholesterol.
Helps remove LDL cholesterol from the arteries and transports it back to the liver for processing.
High levels of HDL cholesterol are associated with a lower risk of heart disease.

Question 71

describe the digestion of proteins

Answer 71

Mouth:
Mechanical breakdown through chewing helps to reduce the size of food particles, making them easier to digest. However, no significant protein digestion occurs in the mouth.

Stomach:
Hydrochloric acid creates an acidic environment that helps to denature proteins, unfolding their complex structures.
Pepsin, an enzyme activated by the acidic environment, begins the breakdown of proteins into smaller polypeptides.

Small Intestine:
Pancreatic enzymes: The pancreas releases enzymes such as trypsin, chymotrypsin, and carboxypeptidase into the small intestine. These enzymes further break down polypeptides into smaller peptides and amino acids.
Intestinal enzymes: The small intestine produces enzymes like aminopeptidase and dipeptidase, which complete the breakdown of peptides into individual amino acids (three, two or one).

Absorption:
Amino acids are actively transported across the intestinal wall into the bloodstream.
Once in the bloodstream, amino acids are transported to the liver and other tissues for use in building new proteins, producing enzymes, and other vital functions.

Question 72

define essential and nonessential amino acids

Answer 72

Essential Amino Acids
Cannot be produced by the body.
Must be obtained through diet.

Nonessential Amino Acids
Can be produced by the body.
Not necessarily required in the diet.

Question 73

how water is absorbed in the digestive system?

Answer 73

The majority of water absorption (92%) takes place in the small intestine. This long, coiled organ is lined with tiny projections called villi, which increase the surface area for efficient absorption. The large intestine also contributes to water reabsorption (7%).

Osmosis: The primary mechanism for water absorption is osmosis. As nutrients are actively transported into the intestinal cells, the concentration of solutes inside the cells increases. This creates an osmotic gradient, drawing water from the intestinal lumen into the cells.

Question 74

what are the functions of vitamins?

Answer 74

Energy metabolism: Many vitamins, such as B vitamins, are involved in converting food into energy.
Growth and development: Vitamins are essential for normal growth and development, including bone health, cell growth, and tissue repair.
Immune function: Vitamins help strengthen the immune system and protect against infections.
Vision: Vitamins A and D are particularly important for maintaining good vision.
Blood clotting: Vitamin K is vital for blood clotting.
Antioxidant protection: Some vitamins act as antioxidants, protecting cells from damage caused by free radicals.
Bone health: Vitamins D and K are essential for bone health.

Question 75

what are the fat soluble vitamins?

Answer 75

Vitamin A: Essential for vision, immune function, and skin health.
Vitamin D: Helps in calcium absorption and bone health.
Vitamin E: Acts as an antioxidant, protecting cells from damage.
Vitamin K: Vital for blood clotting.

Question 76

what’s the normal blood sugar levels?

Answer 76

70-110mg / 100 ml

Question 77

define glucokinase

Answer 77

Glucokinase is an enzyme that plays a crucial role in glucose metabolism, particularly in the liver and pancreas. Its primary function is to catalyze the phosphorylation of glucose to glucose-6-phosphate.
It adds a phosphate group to glucose, which prevents the glucose from leaving the cell.

Question 78

define gluconeogenesis

Answer 78

Gluconeogenesis is a metabolic pathway that results in the biosynthesis of glucose from non-carbohydrate carbon substrates such as lactate, pyruvate, glycerol, and glucogenic amino acids.

The liver is the main organ responsible for gluconeogenesis.

Question 79

how does adrenaline affect the glucose homeostasis?

Answer 79

adrenaline acts to raise blood sugar levels rapidly, providing a quick energy source for the body to respond to stressful situations.

*Stimulates glycogenolysis: Adrenaline promotes the breakdown of glycogen (stored glucose) in the liver and muscles into glucose, releasing it into the bloodstream.
*Inhibits insulin secretion: Adrenaline reduces insulin production, which normally lowers blood sugar levels. This allows for increased glucose availability.
*Enhances gluconeogenesis: Adrenaline indirectly stimulates the liver to produce new glucose from non-carbohydrate sources, further increasing blood glucose levels.
*Reduces glucose uptake: Adrenaline inhibits glucose uptake by tissues like skeletal muscle, preserving glucose for the brain and other vital organs.

Question 80

define enteric nervous system

Answer 80

The enteric nervous system (ENS) is often referred to as the “second brain” due to its complexity and independence. It’s a vast network of neurons embedded in the lining of the gastrointestinal tract.
In the tunica muscularis.

Question 81

what layer of the GI contain blood vessels?

Answer 81

The submucosa layer of the gastrointestinal (GI) tract is the primary location for blood vessels. This layer contains a rich network of blood and lymphatic vessels that supply the mucosa and muscularis layers.

Question 82

define mesenteries

Answer 82

Mesenteries are double folds of peritoneum (the membrane lining the abdominal cavity) that attach the intestines to the posterior abdominal wall. They essentially hold the intestines in place while allowing for some movement.

Support: They anchor the intestines to the abdominal wall.
Vascularization: They contain blood vessels, nerves, and lymphatic vessels that supply the intestines.
Fat storage: They store fat.

Question 83

define retroperitoneal

Answer 83

Retroperitoneal refers to the space behind the peritoneum, the membrane lining the abdominal cavity. Organs located in this space are called retroperitoneal organs.

Includes the kidneys, adrenal glands, pancreas, parts of the large intestine (ascending and descending colon), aorta, and inferior vena cava.