Long Answer Question 2

Question 1

• How do digestive enzymes function to assist absorption of nutrients in the small intestine?
• Include the function of salivary amylase and pepsin. What enzymes are present in pancreatic juice and intestinal juice?
• What do the digestive enzymes break food particles into?

Answer 1

• Digestive enzymes speed up the chemical reactions that involve digestion of the components of food. They are digested to form appropriate nutrient molecules, allowing them to be absorbed into the circulatory/lymphatic system
• Salivary amylase begins digestion of starch in the mouth and pepsin begins digestion of protein in the stomach. Pancreatic amylase, trypsin, nuclease, and lipase are all present in pancreatic juices that enter the small intestine at the duodenum. Maltase, peptidases, and nucleosidases are all secreted from the small intestines in intestinal juice.
• The digestive enzymes will break the food particles up until they resemble glycerol and fatty acids; base, sugar, and phosphate; amino acids; and glucose. These nutrients can be absorbed by the small intestine wall and enter the vessels there

Question 2

Why is water important for digestive enzymes?

Answer 2

Water is a huge part of digestive enzymes because the digestion process requires a hydrolysis reaction - a reaction to degrade polymers where the components of water are added

Question 3

• How is the condition of the small intestine optimal for absorption of nutrients? (2)

Answer 3

• The basic condition in the small intestine is optimal for digestive enzymes that are present from pancreatic juice or from secretions of the intestinal wall.
• The surface area is especially large for effective absorption of nutrients. The walls contain fingerlike projections called villi. Each villus has an outer layer of columnar epithelial cells that have thousands of microscopic extensions called microvilli. Microvilli greatly increase the surface area of the villus for absorption of nutrients.

Question 4

• What vessels do each villus carry?

- Specify which nutrients enter each vessel. (2)

Answer 4

• Each villus also contains blood capillaries and small lymphatic capillary, called a lacteal.
• Glycerol and fatty acids (digested from fats) enter the epithelial cells of villi where they are joined and packaged with lipoprotein droplets that enter the lacteal
• Sugars and amino acids directly enter blood capillaries of villus

Question 5

How does the lymphatic system connect to the circulatory system? (2)

Answer 5

• Villi in the small intestine contain lacteals. Lacteals are a part of the lymphatic system. The lymphatic system is adjunct to the cardiovascular system; so lymphatic vessels carry a fluid called lymph to the cardiovascular veins
• Lymphatic capillaries join to form lymphatic vessels that merge before entering one of two ducts: the thoracic duct or the right lymphatic duct. Thoracic duct drains lymph into the left subclavian vein and the right lymphatic duct drains lymph into the right subclavian vein

Question 6

State the structure of lymphatic vessels that helps it transport lymph.

Answer 6

• skeletal muscles: Movement of lymph is largely dependent on skeletal muscle contraction
• one way valves: lymph forced through vessels from muscular contraction is prevented from flowing backwards by one-way valves

Question 7

• What is the fluid in lymphatic system called?

- State its composition (6) and where they come from

Answer 7

• Fluid in lymphatic capillaries, called lymph, is mostly water, providing fluidity to the lymph.
• Lymph is composed of excess tissue fluid containing solutes (ie. nutrients, electrolytes, and oxygen) derived from plasma and cellular products (ie. hormones, enzymes, and wastes) secreted by cells

Question 8

How does blood assist the digestive system and circulatory system?

Answer 8

Blood transfers nutrients, wastes, and hormones

Question 9

• Why is water important in blood?

- How does water in blood connect to the digestive system?

Answer 9

• Plasma makes up about 55% of blood and 90-92% of plasma is water. Water in blood functions to maintain blood volume and assist in transportation of molecules (acts as a solvent for molecules)
• Water is absorbed from intestines of digestive tract!

Question 10

What controls the movement of fluid through the capillary wall and how do they do so? (2)

Answer 10

Two forces primarily control movement of fluid through capillary wall:

• osmotic pressure, created by salts and plasma proteins, which tends to cause water to move from tissue fluid to blood
• blood pressure, which tends to cause water to move in opposite direction

Question 11

• What occurs at the arterial end of a blood capillary?

- What occurs at the venous end of a blood capillary?

Answer 11

• At arterial end of blood capillary: blood pressure is higher than osmotic pressure so water exits at capillary at this end as net pressure is out
• At venous end osmotic pressure is greater than blood pressure and water tends to move into capillary

Question 12

• What happens at the midpoint of the capillary? (2)

- Where are the nutrients from digestive tract after the capillary-tissue exchange?

Answer 12

• Midway along capillary, where blood pressure is lower, the 2 forces cancel each other out causing no net movement of water
• Solutes now diffuse according to concentration gradient: nutrients (glucose and amino acids from digestive tract) and oxygen diffuse out of capillary, and wastes (carbon dioxide) diffuse into capillary
• Nutrients from digestive tract are now in tissue fluid (the fluid between the cells) where they can supply the cells and keep the human body performing well

Question 13

• Where are capillaries found?

- How is this important and relevant for nutrients coming from the digestive tract?

Answer 13

• Capillaries are found in nearly all regions of the body and serve the cells through exchange of substances across their thin walls
• Nutrients from the digestive tract in blood will travel to cells all over the body and supply them for their needs and processes

Question 14

How does the circulatory system vessels aid the liver in its general function? (2)

Answer 14

• Capillaries that occur in the villi of small intestine pass into venules that join to form the hepatic portal vein
• Vein carries blood with nutrients from intestines to set of capillaries in the liver, an organ that monitors the makeup of blood

Question 15

How does the liver function to monitor the makeup of blood? (5)

Answer 15

• Detoxifies blood by removing and metabolizing poisonous substances
• Makes many plasma proteins, such as albumins and fibrinogen, from amino acids
• Stores glucose as glycogen after a meal, and breaks down glycogen to glucose to maintain glucose concentration of blood between eating periods
• Removes bilirubin, a breakdown product of hemoglobin, from the blood
• Helps regulate blood cholesterol level, converting some to bile salts

Question 16

How does the pancreas help regulate blood glucose levels using insulin? (3)

Answer 16

• The pancreas secretes the hormone insulin from the beta endocrine cells of the pancreatic islets. Insulin is secreted when blood glucose level is high, which usually occurs just after eating.
• It stimulates uptake of glucose by cells, especially liver cells, muscle cells, and adipose tissue (fat) cells. In liver and muscle cells, glucose is then stored as glycogen.
• In all of these ways, insulin will lower the blood glucose level of circulatory system

Question 17

How does the pancreas help regulate blood glucose levels using glucagon? (5)

Answer 17

• The hormone, glucagon, is secreted from pancreas, usually before eating, when blood glucose level is low. Major target tissues of glucagon are liver and adipose (fat) tissue
• Stimulates liver to break down glycogen to glucose
• Adipose tissue cells break down fat to glycerol and fatty acids and liver takes these up and uses them as substrates for glucose formation
• In the muscle cells, breakdown of glucose supplies energy for protein metabolism
• In these various ways, glucagon raises blood glucose level of circulatory system

Question 18

What are the main subtopics of this question? (9)

Answer 18

• digestive enzyme function
• importance of water for enzymes
• small intestine/digestive tracts optimal conditions for absorption of nutrients
• vessels in villus
• lymphatic vessels and their connection to circulatory system, lymph
• importance of blood and water in blood
• capillary-tissue exchange, function and location of capillaries
• livers functions in monitoring makeup of blood
• pancreas function in regulating blood glucose concentration