Digestive System

1. Describe the role of the pancreas and liver in maintaining blood sugar

levels. Answer: Insulin hormone produce by pancreas secretes when blood sugar concentration is high

and causes liver and muscles to take up and store excess glucose as Glycogen. Also promotes

synthesis of protein and fats. LOWERS BLOOD SUGAR LEVEL. Glucagon another pancreatic

hormone secretes when blood sugar concentration is low and causes liver and muscles to break

down glycogen to glucose. Also, stops protein and fat synthesis. RAISES BLOOD SUGAR

LEVEL. In addition, liver stores glucose as Glycogen after eating, and breaks down glycogen to

glucose between eating to maintain the glucose concentration of the blood.

2. Discuss the complete digestion and absorption of starch, proteins and

lipids. Answer;

1- Starch digestion and absorption:

The first stage of digestion of starch begins in mouth. Salivary amylase produced by the salivary

glands and secreted into the mouth and acts on starch to break it into many molecules of maltose.

Maltose is later broken down in the system to glucose. Pancreatic amylase also acts on starch to

convert it to maltose. This process occurs in the duodenum, but amylase is produced by the

pancreas. Maltase produced in the small intestine converts maltose to glucose. Therefore, in two

places starch break downs to maltose: in the mouth by salivary amylase and in the small intestine

by pancreatic amylase. Finally, maltose molecules break down to glucose by maltase in small

intestine. These molecules (glucose) are small enough to absorb directly into blood stream

through the capillaries network of microvilli in intestine; therefore, this stage is absorption

process of glucose molecule.

Physical digestion in mouth

Amylase

Starch + Water-----------> Maltose

-----------> Digestion

Maltase

Maltose + Water -----------> 2 Glucose

Glucose -----------> Absorption (Microvilli’s capillaries network in intestine)

2-Protein Digestion

The first stage of digestion of proteins begins in mouth (mechanical digestion). The chemical

digestion of proteins begins in the stomach where Proteases break down proteins to peptides. There

are two types of proteases: Pepsin which produced by the gastric glands of the stomach and trypsin

which produced by the pancreas. First of all, pepsin enzyme in stomach break downs some protein

molecules, and the remaining protein molecules break downs in small intestine by trypsin which

secreted by pancreas. In these processes, proteins break down to peptides. Peptidases which

produced by the small intestine break down peptides into amino acids. These molecules (Amino

Acids) are small enough to absorb directly into blood stream through the capillaries network of

microvilli in intestine; therefore, this stage is the absorption process of amino acids molecules.

3-Lipid Digestion

The first stage of digestion of lipids begins in the mouth (mechanical digestion). Bile produced by

the liver stored in the gall bladder breaks down fat in the duodenum into fat droplets (mechanical

digestion). The breaking down of fats to fat droplets by bile called emulsification. Lipase produced

by the pancreas breaks down fat droplets into glycerol and 3 fatty acids (chemical digestion). These

molecules (fatty acids and glycerol) are small enough to absorb directly into lacteal system in

intestinal microvillus. So fatty acids enter the lacteals which will go back into the bloodstream

later at the Subclavian veins.

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3. How is the structure of the small intestine suited to its function? Answer: The small intestine is specialized for absorption in that the small intestine is long

with convoluted wall (folded walls). The structure of the small intestine contains millions

of microscopic folds which act to increase the surface area. The walls of the small intestine

have villi (finger-like projections along the walls). The villi themselves have tiny microvilli

on columnar epithelial cells. Within each villus are blood vessels and small lymph vessel

called a lacteal which absorbs fluids and returns it to the veins. Absorption occurs across

the walls of each villus by active transport (uses energy). Glucose and Amino acids enter

the blood vessels and travel to the liver. Glycerol and fatty acids enter the lacteals, which

will go back into the bloodstream later at the Subclavian veins.

4. Name the structures food passes through all the way from the mouth to

the anus.

This picture depicts all organs which are related to the digestive system.

The second one shows the pathway of food from the mouth to the anus. It should be

mention that normally the foods do not pass through the appendix.

5. Describe 4 functions of the liver.

Answer:

1. Destroys old red blood cells and converts hemoglobin to a product in bile.

2. Produces Bile that is stored in the gall bladder before entering the Duodenum where it

emulsifies fat.

3. Store Glucose as Glycogen after eating, and breaks down glycogen to glucose between

eating to maintain the glucose concentration of the blood.

4. Produces Urea from the breakdown of amino acids (deamination)

5. Makes Blood Proteins from amino acids.

6. Detoxifies the blood by removing poisonous substances and metabolizing them (converting

them to harmless substances).

6. How is the structure of the stomach suited to its function?

Answer:

The stomach is an expanded section of the gastrointestinal tract between the esophagus and the

duodenum of the small intestine. Stomach is a J-shaped organ which stores and churns food. The

churning helps physically digest food, which creates more surface area and results in a mushy

liquid called acid chyme. The inside of the stomach is composed of three layers, from the innermost

layer to the outermost layer: mucosa, sub-mucosa, muscularis externa, and the serosa. The mucosa

is where stomach acid is produced and secreted into the stomach. The sub-mucosa is layer

composed of connective tissue that separates the mucosa from the muscularis externa. The

muscularis externa is composed of three layers of smooth muscle: inner oblique, middle circular,

and outer longitudinal. These are the muscles that are primarily responsible for mixing material

that has come into stomach with digestive enzymes and moving the material through the stomach.

The final layer is the serosa, which is a layer of connective tissue that attaches and is continuous

with the peritoneum, the lining of the abdominal cavity. The stomach has a muscular folded tissue

contains gastric glands which secret pepsin, HCl, and mucus. Pepsin is an enzyme which digests

proteins. HCl makes the stomach environment acidic, and mucus protects stomach tissue from

burn due to acidic property of HCl. The pyloric sphincter at the end of the stomach controls the

amount of chyme that leave stomach into the small intestine. The acidic environment of stomach

kills the bacteria. The chemical digestion of proteins beings here. Gastrin is a hormone produced

by the lower part of the stomach which enters the blood stream and later stimulate the upper part

of the stomach to stimulate gastric glands to produce Pepsinogen and HCl. HCl and pepsinogen

react with each other to produce Pepsin. Pepsin chemically digests proteins to peptides. HCL can

burn the gut lining so a mucous layer is produced to prevent this from happening. If a portion of

the gut is burned it is called an ulcer. Pyloric Sphincter - Band of muscle which closes off the

lower part of the stomach and only allows small amounts (~1 teaspoon) of chyme to enter the small

intestine.

As a result, muscular structure of stomach helps physical digestion of food, while secretory portion

of stomach in one hand helps in chemical digestion, and on the other hands regulated its secretion

by different mechanism. Also, mucosal secretion of stomach protects it from burn by HCL.

………………………………………………………….

Respiratory System

1. Explain why breathing happens.

Answer:

The sole reason of breathing is maintain the correct concentration of oxygen. Without oxygen we

will die. The Respiratory System supplied the body with oxygen for tis energy production.

Without Oxygen, the body shuts down in minutes. The Respiratory System works closely with

the Circulatory System. CO2 concentration and H+ concentration are the PRIMARY STIMULI

that cause us to breathe. When Carbon Dioxide and/or Hydrogen ion concentration gets too high,

the Breathing center in the Medulla Oblongata is stimulated.

1. A nerve impulse is sent from the Medulla Oblongata to the diaphragm and rib cage.

2. The diaphragm contracts and lowers; the rib muscles contract (intercostal muscles) and

raise the ribs. These actions increase the size of the chest cavity. Increased volume,

decreases pressure.

3. A partial vacuum is created in the lungs (air pressure in the lungs is reduced).

4. Air Rushes into the lungs from outside in order to rebalance the pressure. This is the

process of inspiration.

In addition to the Respiratory Center in the Medulla Oblongata, there are other receptors

that can respond to stimuli:

a. Carotid bodies - in the carotid artery

b. Aortic bodies - in the aorta

These respond to high concentration of Hydrogen Ions but can also respond to levels of

carbon dioxide in the blood.

2. How the upper respiratory track is kept free of debris?

Answer: Cleansed of debris. This is a two-part process:

a. The initial cleaning is by the nose hairs and mucous in the nasal Passageways.

b. The second is the process that occurs further along were the accumulation of debris can no

longer get out of through the nose. This is the role of the mucous lining and the cilia along the

trachea and the bronchi. Pretty well any material other than the gasses of the inhaled air will get

caught in the mucous. The cilia are in constant motion beating the debris-laden mucous upward

towards the pharynx. When this material is detected at the back of the mouth, it is swallowed (or

coughed up and spit out)

3. Describe exhalation Answer:

- Expiration - Expelling Carbon Dioxide

1. When the lungs are full, stretch receptors in the alveoli are stimulated

2. The Medulla Oblongata is notified and stops sending messages.

3. The diaphragm and rib muscles relax.

4. The chest cavity gets smaller. Decreasing volume, which increases the pressure in the

lungs. Air is forced out.

4. Describe inhalation

Answer:

- Inspiration - Bringing Oxygen into the lungs

CO2 concentration and H+ concentration are the PRIMARY STIMULI that cause us to

breathe. When Carbon Dioxide and/or Hydrogen ion concentration gets too high, the

Breathing center in the Medulla Oblongata is stimulated.

A nerve impulse is sent from the Medulla Oblongata to the diaphragm and rib cage.

The diaphragm contracts and lowers; the rib muscles contract (intercostal muscles) and

raise the ribs. These actions increase the size of the chest cavity. Increased volume,

decreases pressure.

A partial vacuum is created in the lungs (air pressure in the lungs is reduced).

Air Rushes into the lungs from outside in order to rebalance the pressure. This is the

process of inspiration.

5. How is the structure of the alveoli suited to their function? Answer:

Area where gas exchange occurs is alveoli. They are very numerous. Up to 300 million alveoli in

the human lung. This provides a great surface area for diffusion of gases. They are very thin-

walled (one cell) Alveolar walls are only one cell thick. This aids in diffusion. The alveoli have a

coating of lipoprotein on their inner surface. This helps to maintain surface tension thus

preventing them from collapsing and sticking together during exhalation. They are supplied with

stretch receptors. These are nerve endings that are sensitive to stretch. During inhalation, these

signal when the alveoli are full enough (stretched). This marks the onset of exhalation. The

alveoli surfaces have a very rich blood supply from the pulmonary capillaries to ensure

maximum diffusion. They are highly vascularized. Made up of Squamous (flat) Epithilial cells.

………………………..

Circulatory System

1. Describe the structure/function/produced where of the red blood cells,

white blood cells, platlets.

Answer:

1. Red Blood Cells - Erythrocytes

Live about 120 days.

Produced in Red Bone Marrow (In skull, ribs, vertebrae, and long bones.)

Myeloid stem cells form RBC. These stem cells are called Erythroblasts. Erythroblasts

will differentiate into Erythrocytes.

Produces about 5 million every second.

RBC contains a protein called Hemoglobin. Hemoglobin contains iron (gives blood its

red color). Picks up oxygen in the lungs (cooler blood). It combines with oxygen in the

lungs and releases it in the warmer tissues. Approximately 200,000,000 hemoglobin

molecules in one RBC. If hemoglobin was not packaged up in RBC, oxygen would leak

out of circulatory system.

RBC allow the blood to remain liquid so the heart does not have to work as hard.

Destroyed in the liver and spleen.

2. White Blood Cells - Leukocytes

Larger than RBC

They have nucleus (RBC do not)

less numerous than RBC (700:1)

Do not have a definite shape.

Function: Fights against infection

Phagocytic

Produce Antibodies

3. Platelets - (Thrombocytes)

Produce 2 billion a day.

Broken fragments of larger cells.

Very important role in blood clotting.

o Blood Clotting - Need three things in blood 1. Prothrombin

2. Fibrinogen

3. Platelets

Platelets clump at the site of the "leak" and partially close it.

The platelets and the injured tissue together release an enzyme called

THROMBOPLASTIN.

……………….

2. Describe the structure/function – arteries, veins, capillaries

Answer:

Arteries:

Function: Largest are elastic (aorta & pulmonary). They stretch when the ventricles

eject the blood from the heart, then recoil, moving blood along. Large arteries

branch to form smaller arteries called arterioles. Transport blood away from the

heart.

Structure: Thick muscular, elastic walls.

Location: Usually found deep along bones

Veins:

Function: Transports blood back to the heart.

Structure: Thin walls; contain valves.

Location: Often on the surface surrounded by skeletal muscle.

Capillaries:

Function: Interconnect arteries to veins.

Structure: Very thin walls (1 cell thick).

Location: Everywhere; within a few cells of each other.

Capillaries have sphincter muscles that can dilate and constrict the vessel. If all

capillary beds were open at one time, it would decrease the blood pressure. If all the

capillary beds were closed, it would increase blood pressure.

3. Be able to name specific arteries and veins and their function

Aorta: This is the major blood vessel carrying oxygenated blood out of the heart. It leaves

the left ventricle, loops over top of the heart creating the structure known as the aortic arch

and descends along the inside of the backbone.

Function: Branches from this blood vessel feed the rest of the body.

Coronary Arteries and Veins:

The very first branches off the Aorta are the Coronary arteries. These relatively small

blood vessels can be seen on the surface of the heart.

Function: Feeds the heart muscle. (The heart does not receive its nutrients from the blood

that travels through it. The muscle is too dense and thick and the blood is traveling through

it too hard and fast.) Coronary Vein takes the "spent blood" back to the heart.

Carotid Arteries:

These branches

off the aortic

arch and take

the blood to the

head including

the brain.

Function: They

are highly

specialized in

that they

contain a

number of

different types

of nerve

endings:

Chemoreceptors that detect oxygen content, and Pressure Receptors that detect blood

pressure changes. These chemoreceptors help to maintain homeostasis.

Jugular Veins:

The match for the Carotid Artery. They do not contain valves. Blood flow is through

gravity.

Function: They conduct blood out of the head to the Superior Vena Cava.

Subclavian Arteries and Veins:

Also branch from the Aorta. Travels under the Clavicle.

Function: Branch to feed the arms (brachial artery). Veins collect blood from the arms.

Mesenteric Arteries:

These arteries branch off from the aorta as it travels posteriorly. They go to the intestines

where they branch into capillaries that can be identified as villi. For the purpose of this

course there is no corresponding mesenteric vein.

Function: Feeding the organs of the digestive system and picks up newly digested nutrients

in the body.

Hepatic Portal Vein:

Instead of a mesenteric vein, it is called a hepatic portal vein. Hepatic means liver; portal

indicates that there is a capillary bed on both ends of it.

Function: Brings blood from digestive tract to liver.

Hepatic Vein:

Once the liver has done its thing to the blood, the blood must return to the venous system.

Function: Carries blood from the liver to the posterior Vena Cava.

Renal Arteries and Veins:

The Renal Arteries branch off the dorsal aorta as it passes through the lumbar region of the

body.

Function: the arteries take blood to the kidneys while the renal veins take blood away

from the kidneys and back to the posterior Vena Cava.

Iliac Arteries and Veins:

When the dorsal aorta gets to the pelvic area. It branches into two Iliac Arteries, one goes

down each leg. Off the Iliac Arteries is another branch that feeds the upper leg. This is

called the Femoral Artery.

Function: To supply the legs with oxygenated blood and return deoxygenated blood to the

Posterior Vena Cava.

Anterior (Superior) and Posterior (Inferior) Vena Cava:

The largest vein of the body.

Function: Large vein that collects all the "spent" blood from smaller veins and carries it to

the heart (right atrium). The Anterior Vena Cava collects blood from the Upper body,

while the Posterior Vena Cava collects blood from the lower body.

Pulmonary Veins and Arteries:

The Pulmonary Circuit is comprised of the pulmonary trunk and arteries that deal strictly

with the heart and the lungs. It is the only artery in the body that carries deoxygenated

blood and the only vein in the body that carries oxygenated blood. (remember the function

of arteries is to carry blood away from the heart and the function of veins is to carry blood

to the heart)

Function: The arteries bring deoxygenated blood from the right side of the heart to the

lungs to get oxygen for the body, while the veins return oxygenated blood from the lungs

to the left atrium of the heart.

4. Explain the changes in blood pressure and velocity through the blood

vessels.

Answer Cross sectional area of the blood vessels (sum of the cross sectional area of all blood

vessels of one type) has a major effect on blood flow. As cross sectional area increases,

velocity of the blood decreases. Velocity of the blood decreases from aorta to arteries to

capillaries and increases in venules and veins. As CSA increases blood pressure

decreases. Once the blood pressure is lost in the capillaries it cannot be regained even

though CSA of venules and veins increases.

……………….

5. Contrast pulmonary vs. Systemic circulation (include comparison of gas

content)

Answer:

Pulmonary Circuit:

Path that goes to and from the lungs.

From right ventricle through the pulmonary trunk--pulmonary arteries--lung capillaries--

pulmonary veins--left artium.

Carries carbon dioxide filled blood to lungs for cleaning.

Returns oxygen rich blood to heart.

Systemic Circuit:

Path from left ventricle to

body back to right atrium of heart.

Carries oxygen rich blood to

the body tissues.

Returns carbon dioxide filled

blood to the heart.

6. Describe 3 functions of haemoglobin. Answer:

Hemoglobin contains iron (gives blood its red color), and picks up oxygen in the lungs (cooler

blood). The main function of hemoglobin is to carry oxygen from the lungs to all the tissues of

the body. Also, some of carbon dioxide is transported from tissues to lungs through hemoglobin.

It combines with oxygen in the lungs and releases it in the warmer tissues. If hemoglobin was not

packaged up in RBC, oxygen would leak out of circulatory system.

In short, “(1) hemoglobin as molecular heat transducer through its oxygenation-deoxygenation

cycle, (2) hemoglobin as modulator of erythrocyte metabolism, (3) hemoglobin oxidation as an

onset of erythrocyte senescence, (4) hemoglobin and its implication in genetic resistance to

malaria, (5) enzymatic activities of hemoglobin and interactions with drugs, and (6) hemoglobin

as source of physiological active catabolites”( Giardina et al,1995 ).

7. Describe fetal circulation – special features/function

Answer:

Fetal systems have FOUR features not present in adult systems:

1. OVAL OPENING

Oval opening is an opening between the 2 atria; it is covered by a flap of tissue that acts like a

valve. Blood flows directly from the right atrium to the left atrium and allowing blood to bypass

the lungs, which do not work yet.

2. ARTERIAL DUCT

Arterial duct is a connection between the Pulmonary Artery and the Aorta. Blood flows from the

Pulmonary Artery to the Aorta, again allowing blood to bypassing the lungs.

3. UMBILICAL ARTERY AND VEIN

Umbilical Artery takes waste (Carbon Dioxide and Urea) to the Placenta from the fetus.

Umbilical Vein takes nutrients (Oxygen and Glucose and Amino Acids) to the Fetus from the

Placenta.

4. VENOUS DUCT

Venous duct is a connection between the Umbilical Vein and the Vena Cava. Blood coming from

the umbilical vein passes directly to the vena cava through the venous duct allowing blood to

bypass the liver.

8. Define systole vs. Diastole Answer:

Contraction of the heart is a two steps process. The term systolic pressure (or Systole) refers to

the pressure when the ventricles contract. This is the highest blood pressure reading.

The term diastolic pressure (diastole) refers to the blood pressure when the heart is at rest. This is

the lowest blood pressure reading.

9. Describe the tissue/fluid exchange Answer:

Blood is oxygenated as it passes through lung tissue. Oxygen (higher in concentration in the

inhaled air) diffuses through the thin walled tissues of the lung to capillaries and into the blood

where it bonds to hemoglobin (the iron containing protein that is part of the RBC). A single

hemoglobin molecule has four bonding sites for oxygen and is called oxyhemoglobin when

transporting oxygen.The blood reaches arterioles and then the capillaries where blood pressure

decreases. Nutrients (products of digestion) and oxygen diffuse into the tissues. The larger

particles in blood stay where they are because they are too big to get out. Because of these large

molecules, the blood is said to be hypertonic to the tissues. As a result, the water from the tissues

is drawn back into the venule side of the capillary bed. When the fluid returns it carries carbon

dioxide and wastes with it. Blood pressure on arteriole side of the capillary bed is higher than

osmotic pressure and will try and push substances such as oxygen, water, glucose and amino

acids out of blood into the tissues of the body.Blood pressure on the venule side of capillary is

lower than the osmotic pressure and therefore wastes such as Carbon Dioxide, ammonia and

water are forced from the tissues of the body into the blood.

10. Explain the hearts nervous control over heart rate.

Answer:

The rate of the heart can also be controlled by the nervous system.

The heart rate center is located in the Medulla Oblongata of the brain. The SA Node is

connected to the brain by the Vagus nerve (cranial nerve #10). This nerve pathway, part of

the Autonomic Nervous System (not under conscious control), has two system that affect the

Heart Rate:

1. Parasympathetic System - Causes the heart beat to slow down.

2. Sympathetic System - Causes the heart beat to increase during times of stress.

Factors such as need for oxygen or the blood pressure level determine which of these

systems become active. When the brain perceives that the blood is getting delivered to

the tissues too slowly, or if blood pressure is low, the brain will signal the SA Node to

speed up its contraction.

11. Describe the structure of the heart and function of the structures. Answer:

Left and Right Atria - Collecting Chambers

Right: Collects blood from Vena Cava.

Left: Collects blood from Pulmonary Veins.

Left and Right Ventricles - Pumps

Right: Sends blood to the lungs via the Pulmonary Trunk.

Left: Sends blood to the body via the Aorta

Atrioventricular Valves - Valves between the atria and ventricles.

Prevent backflow of blood

Right hand side ¨Tricuspids¨ - three cusps, or flaps

Left hands side ¨bicuspid¨ - two cusps

Chordae Tendineae - Strong, Fibrous strings that support the A.V. Valve.

Keeps the valves from inverting with the force of blood flow.

Semi-Lunar Valves - Between ventricles and arteries exiting heart.

Prevents back flow of blood from Pulmonary Trunk into right ventricle.

Prevents back flow of blood from aorta into left ventricle.

Pulmonary Trunk - Branches off to form the Pulmonary Arteries.

Receives blood from the right ventricle.

Septum - The wall of the Heart.

Separates the left and right sides of the Heart

…………………………………..

12. Be sure to be able to trace the flow of blood around the body eg. Head to

small intestine.

Answer:

Jugular vein to vena cava, vena cava to right atrium, right atrium to right ventricle, right

ventricle to pulmonary artery, pulmonary artery to the lung, lung to the pulmonary vein,

pulmonary vein to the left atrium, left atrium to the left ventricle, left ventricle to the aorta, aorta

( abdominal aorta)to the mesenteric artery. Oxygenated blood leaves the heart through the aorta,

which descends into the abdominal cavity as the abdominal aorta. The superior mesenteric artery

supplies the whole small intestine and extends branches up to the middle third of the transverse

colon.

13. Describe the lymphatic system structure/function. Answer:

Functions of the Lymphatic System:

1. Takes excess tissue fluid and sends it to the circulatory System. The Lymphatic System

joins the Circulatory System at the subclavian veins.

2. Products of fat digestion are absorbed into Lacteals, which lead to the Lymph Vessels

and Nodes.

3. Lymph Nodes produce Lymphocytes (a type of White Blood Cell).

4. Lymph Nodes act as filters and trap bacteria and other debris (helps to purify the body

fluids), attacks foreign substance (bacteria or viruses).

5. Lymphocytes produce antibodies. Each antibody fights a specific antigen (foreign

protein). Antigens are proteins found in the outer membrane of blood and it is the type of

protein found that determines the type of blood. Antibodies are proteins that attack

unwanted proteins which results in agglutination.

Antigen + Antibody --> Inactive complex.

Key Lymphatic Structures

Spleen:

Largest lump of Lymphatic Tissue.

Produces Lymphocytes and stores excess blood.

If your blood pressure is high, it stores blood so that blood pressure lowers.

If your blood pressure is low, it contracts and adds blood to the circulatory system, so that

blood pressure rises.

Thymus Gland:

Bi-lobed structure which is important in the maturing of some Lymphocytes.

Becomes smaller with age.

Tonsils and Appendix:

Also contain Lymphoid Tissue.

Thought to help remove invading organisms and viruses.

Lymphatic Tissue:

Produce lymphocytes and stores excess blood.

Structures in the Lymphatic System

Lymph Vessels:

Similar to veins, but fluids only travel in one direction. Contain lymph veins and

capillaries, but NO lymph arteries.

Lymph Nodes:

Small oval or round tissues which filter fluids and produce Lymphocytes.

Lacteals:

Blind sacs in villi of Digestive System which absorb products of Fat Digestion.

…………………..

Reference: Giardina, B., Messana, I., Scatena, R., & Castagnola, M. (1995). The multiple functions of hemoglobin. Crit Rev Biochem

Mol Biol, 30(3), 165-196. doi: 10.3109/10409239509085142