REVIEW SHEET FOR EXAM2

Chapter 4: Organization and Regulation of Body Systems

1. What is a tissue?A tissue is composed of specialized cells of the same type that perform a common function in the body.

2. Know the names of four types of tissuesConnective, Muscular, Nervous and Epithelial.

3. How cancers are classified?According to the type of tissue from which they arise (Sarcomas = muscular and connective; Leukemia = blood; Carcinomas = epithelial).

4. What are the functions of connective tissues?Bind and support parts of the body.

5. What all types of connective tissue have?Three components: specialized cells, ground substance and protein fibers

6. What are the types of fibers?Collagen fibers (contain collagen, a protein that gives them flexibility and strength), reticular fibers (very thin collagen fibers, highly branched proteins that form delicate supporting networks) and elastic fibers (fibers that contain elastin, a protein that is not as strong as collagen but is more elastic).

7. What are the different types of connective tissues?It varies in consistency: solid (bone), semifluid (cartilage) and fluid (blood), but the three main types of connective tissue are supportive (bones and cartilage), fibrous (Loose and dense) and fluid (blood and Lymph).

8. Talk about the three types of connective tissues.Fibrous Connective Tissue: Fibrous tissue exists in two forms: loose fibrous tissue and dense fibrous tissue. Both connective tissues have cells

called fibroblasts located some distance from one another and separated by a jellylike ground substance containing white collagen fibers and yellow elastic fibers. Matrix is a term that includes ground substance and fibers. Loose fibrous connective tissue, also called areolar tissue, supports epithelium and many internal organs. Its presence in lungs, arteries, and the urinary bladder allows these organs to expand. It forms a protective covering enclosing many internal organs, such as muscles, blood vessels, and nerves. Adipose tissue is a special type of loose connective tissue in which the cells enlarge and store fat. Dense fibrous connective tissue contains many collagen fibers packed together. This type of tissue has more specific functions than does loose connective tissue. Is found in tendons, which connect muscles to bones, and in ligaments, which connect bones to other bones at joints.

Supportive Connective Tissue: Cartilage and bone are supportive connective tissues. In cartilage, the cells lie in small chambers called lacunae (sing., lacuna), separated by a solid, yet flexible, matrix (semisolid). Unfortunately, because this tissue lacks a direct blood supply, it heals slowly. Bone is the most rigid connective tissue. It consists of an extremely hard matrix of inorganic salts, notably calcium salts. These salts are deposited around protein fibers, especially collagen fibers. The inorganic salts give bone rigidity. The protein fibers provide elasticity and strength, much as steel rods do in reinforced concrete.

Fluid Connective Tissue: The body has two fluid connective tissues: blood and lymph. Blood, which consists of formed elements and plasma, is located in blood vessels. Blood transports nutrients and oxygen to tissue fluid. Tissue fluid bathes the body’s cells and removes carbon dioxide and other wastes. Blood helps distribute heat and also plays a role in fluid, ion, and pH balance. Lymph is a clear, watery, sometimes faintly yellowish fluid derived from tissue fluid. It contains white blood cells. Lymphatic vessels absorb excess tissue fluid and various dissolved solutes in the tissues. They transport lymph to particular vessels of the cardiovascular system. Lymphatic vessels absorb fat molecules from the small intestine. Lymph nodes, composed of fibrous connective tissue, occur along the length of lymphatic vessels. Lymph is cleansed as it passes through lymph nodes, in particular, because white blood cells congregate there. Lymph nodes enlarge when you have an infection.

9. What are the functions of Muscular tissues?Move the body and its parts. It is specialized to contract.

10. What are muscle fibers?Cells that contain actin and myosin filaments. The interaction of these filaments accounts for movement.

11. What is striation?Actin and myosin arranged in an order.

12. What are the three different types of Muscular tissues?Skeletal: It is founded attached to the bones, its structure is cylindrical and long, has striation, is multinucleated and its action is voluntary.Smooth: It is founded in walls of the heart, its structure is short and branched, has striation, has a single centrally located nucleus and its action

is involuntary.

Cardiac: It is founded in the walls of viscera and blood vessels, its structure is a spindle shape, do not has striation, has a not centrally located nucleus and its action is involuntary.

13. What are the functions of Nervous tissues?Nervous tissue is the central component of the nervous system, which serves three primary functions in the body: sensory input, integration data and motor output, in other words, communication.

14. What are the different cells of the Nervous tissues and what are their functions?Neurons: Neuroglia are cells that outnumber neurons nine to one and take up more than half the volume of the brain. Although the primary

function of neuroglia is to support and nourish neurons, research is being conducted to determine how much they directly contribute to brain function.

Neuroglia: A neuron is a specialized cell that has three parts: dendrites, a cell body, and an axon (Fig. 4.6). A dendrite is an extension that receives signals from sensory receptors or other neurons. The cell body contains most of the cell’s cytoplasm and the nucleus. An axon is an extension that conducts nerve impulses. The nervous system has three functions: sensory input, integration of data, and motor output.

15. What are the functions of epithelial tissues?The epithelial tissue consists of tightly cells that form a continuous layer. It covers surfaces and lines body cavities and usually has a protective function, but it can be modified to carry out secretion, absorption, excretion and filtration.

16. What are the different types of epithelial tissues?Simple Epithelia: Epithelial tissue is either simple or stratified. Simple epithelia have only a single layer of cells and are classified according to

cell type.Stratified Epithelia: Stratified epithelia have layers of cells piled one on top of the other. Only the bottom layer touches the basement membrane.

The nose, mouth, esophagus, anal canal, the outer portion of the cervix (adjacent to the vagina), and vagina are lined with stratified squamous epithelium.

17. What are the regions of the skin? Skin consists of two regions: the epidermis and the dermis. A subcutaneous layer, called hypodermis, lies below the dermis. The epidermis is the skin layer that is visible, covering the entire body from head to toe. It contains stem cells, which produce new epithelial cells. The dermis is the hub of all operations in the skin where a lot of action takes place. It is tucked away between the epidermis and hypodermis and it is the layer that holds all the blood vessels, nerves, hair follicles, collagen and sweat glands. The hypodermis is the layer that has the main job of temperature control. This is because fatty deposits and collagen are found here, which insulate our bodies and make sure that we stay warm. The hypodermis is also where adipose tissues are found.

18. What is Homeostasis?Is the body’s ability to maintain a relative constancy of its internal environment by adjusting its physiological process.

19. What is negative and positive feedback? (Know examples of each.)Negative Feedback: Negative feedback mechanisms keep the environment relatively stable. When a sensor detects a change above or below a

set point, a control center brings about an effect that reverses the change and brings conditions back to normal again. Examples include regulation of blood glucose level by insulin, regulation of room temperature by a thermostat and furnace, and regulation of body temperature by the brain and sweat glands.

Positive Feedback: In contrast to negative feedback, a positive feedback mechanism brings about rapid change in the same direction as the stimulus and does not achieve relative stability. These mechanisms are useful under certain conditions, such as during birth. Ex.: Blood clothing.

Chapter 5: Cardiovascular System: Heart and Blood Vessels

1. What is the function of the cardiovascular system?Transport: oxygen, carbon dioxide and other wastes products, nutrients, and hormones.Protection: cells of the immune system are transported to help protect the body from infection.Regulation: maintain homeostasis of a variety of the body’s conditions.

2. What are the two components of the cardiovascular system and their functions?The cardiovascular system consists of the heart and blood vessels. The heart pumps blood and blood vessels take blood to and from capillaries, where exchanges of nutrients for wastes occur with tissue cells. Blood is refreshed at the lungs, where gas exchange occurs; at the digestive tract, where nutrients enter the blood; and the kidney, where wastes are removed from blood.

3. What is the main pathway of blood in the body?Heart – arteries – arterioles – capillaries – venules – veins – back to the heart…

4. What are the types of blood vessels?Arteries: Are blood vessels that take blood away from the heart. Arteries have the thickest walls, which allows them to withstand blood pressure.

They have are three layer: thin inner epithelium, thick smooth muscle layer and outer connective tissue. Arterioles are small arteries that regulate blood pressure.

Capillaries: Are microscopic vessels between arterioles and venules made of one layer of epithelial tissue, where exchange of substances occurs.

Veins: Veins take blood to the heart. They have relatively weak walls with valves that keep the blood flowing in one direction. Venules are small veins that receive blood from the capillaries. Venule and vein walls have 3 layers: thin inner epithelium, thick smooth muscle layer and outer connective tissue

5. What is the lymphatic system?Is the system that assists the cardiovascular system because lymphatic vessels collect excess tissue fluid and return it to the cardiovascular system.

6. Know the structure of the heart.The heart is a large, muscular organ consisting of mostly cardiac tissue called the myocardium and surrounded by a sac called the pericardium. It has four chambers. The two chambers on the right are separated from the two chambers on the left by a septum. The right side pumps the blood to the lungs and the left side pumps blood to the rest of the body. Intercalated disks contain gap junctions and these allow muscle cells to simultaneously contract. Desmosomes at the same location allow the cells to bend and stretch. The heart has also two sets of valves (semilunar valves and atrioventricular valves). Valves produce the “lub” and “dub” sounds of the heartbeat.

7. What is the path of blood through the heart and body?

The superior vena cava and the inferior vena cava carry oxygen-poor blood from body veins to the right atrium. The right atrium contracts, sending blood through an atrioventricular valve (the tricuspid valve) to the right ventricle. (Remember, the left atrium

contracts at the same time.) The right ventricle contracts, pumping blood through the pulmonary semilunar valve into the pulmonary trunk. The pulmonary trunk, which

carries oxygen-poor blood, divides into two pulmonary arteries, which go to the lungs. Pulmonary capillaries within the lungs allow gas exchange. Oxygen enters the blood; carbon dioxide waste is excreted from the blood. Four pulmonary veins, which carry oxygen-rich blood, enter the left atrium. The left atrium pumps blood through an atrioventricular valve (the bicuspid [mitral] valve) to the left ventricle.

The left ventricle contracts, sending blood through the aortic semilunar valve into the aorta. (The right ventricle is contracting at the same time.) Large arteries, smaller arteries, and arterioles supply tissue capillaries. Tissue capillaries drain into increasingly larger veins. Veins drain into

the superior and inferior vena cava, and the cycle starts again.

8. What are the functions of the four chambers of the heart?The right atrium receives oxygen-poor blood from the body and pumps it to the right ventricle.The right ventricle pumps the oxygen-poor blood to the lungs.The left atrium receives oxygen-rich blood from the lungs and pumps it to the left ventricle.The left ventricle pumps the oxygen-rich blood to the body.

9. How is the heartbeat controlled?Internal control: The SA node in the right atrium initiates the heartbeat and causes the atria to contract. This impulse reaches the AV node, also

in the right atrium, to send a signal down the AV bundle and Purkinje fibers that causes ventricular contraction. These impulses travel between gap junctions at intercalated disks.

External control: Heartbeat is also controlled by a cardiac center in the brain and hormones such as epinephrine and norepinephrine.

10. What is the name of the artery that supplies blood to the heart muscles?Coronary.

11. What is the function of valves in a vein?Allow blood to flow only toward the heart when open and prevent the backward flow of blood when closed. Valves are found in the veins that carry blood against the force of gravity, especially the veins of the lower extremities.

12. Which vein brings low oxygen content blood to the right atrium?Vena cava.

13. What is the name of the blood vessel that carry deoxygenated blood to the lungs for oxygenation?Pulmonary arteries.

14. What is the name of the largest artery?Aorta.

15. Which part of the heart sends oxygenated blood through the aorta?Left ventricle.

16. What is the function of SA node and AV node?The SA node sends out a stimulus (black arrows), which causes the atria to contract. When this stimulus reaches the AV node, it signals the ventricles to contract. The electrical signal passes down the two branches of the atrioventricular bundle to the Purkinje fibers. Thereafter, the ventricles contract

17. What do you mean by systolic pressure and diastolic pressure? What happens during systole and diastole?Blood pressure is the pressure of blood against the wall of the blood vessel. A sphygmomanometer (blood pressure instrument) can be used to measure blood pressure, usually in the brachial artery of the arm. The highest arterial pressure, called the systolic pressure, is reached during ejection of blood from the heart. The lowest arterial pressure, called the diastolic pressure, occurs while the heart ventricles are relaxing. Normal resting blood pressure for a young adult should be slightly lower than 120 mm Hg over 80 mm Hg, or 120/80, but these values can vary somewhat and still be within the range of normal blood pressure. Therefore, during systole, the atria contract together followed by the ventricles contracting together. This is followed by diastole, a rest phase, when the chambers relax.

18. What are the structural and functional differences between an artery and a vein? Arteries: The arteries are more muscular than veins to withstand the higher pressure exerted on them; Vessels carry body from the heart to

various body parts; arteries carry oxygenated blood from the heart except pulmonary artery; arteries have thick elastic muscular walls; valves are absent; blood flows under high pressure.

Vein: Vessels carry blood from various body parts to the heart; Veins carry deoxygenated blood from the various body parts except pulmonary vein; veins have thin non elastic muscular walls (thinner wall and a larger center to contain blood); valves are present to prevent the backward flow of blood; blood flows under low pressure.

19. What is an electrocardiogram (ECG)? Know about the P, QRS and T waves.Is a recording of the electrical changes that occur in myocardium during a cardiac cycle. Body fluids contain ions that conduct electric currents. Therefore, the electrical changes in myocardium can be detected on the skin’s surface. A normal ECG indicates that the heart is functioning properly. The P wave occurs just prior to atrial contraction; the QRS complex occurs just prior to ventricular contraction; and the T wave occurs when the ventricles are recovering from contraction.

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20. What are the cardiovascular pathways?Pulmonary circuit: In the pulmonary circuit, blood travels to and from the lungs. Blood from all regions of the body fi rst collects in the right

atrium and then passes into the right ventricle, which pumps it into the pulmonary trunk. The pulmonary trunk divides into the right and left pulmonary arteries, which branch as they approach the lungs. The arterioles take blood to the pulmonary capillaries, where carbon dioxide is given off and oxygen is picked up. Blood then passes through the pulmonary venules, which lead to the four pulmonary veins that enter the left atrium. Blood in the pulmonary arteries is oxygen-poor but blood in the pulmonary veins is oxygen rich, so it is not correct to say that all arteries carry blood high in oxygen and all veins carry blood low in oxygen (as people tend to believe). Just the reverse is true in the pulmonary circuit.

Systemic circuit: In the systemic circuit, the aorta divides into blood vessels that serve the body’s organs and cells. The aorta, receives blood from the heart, and the largest veins, the superior and inferior venae cavae, return blood to the heart. The superior vena cava collects blood from the head, the chest, and the arms, and the inferior vena cava collects blood from the lower body regions. Both enter the right atrium

21. Give examples of cardiovascular diseases and their prevention.Hypertension, Atherosclerosis, stroke, heart attack and aneurysm. The prevention can be done avoiding tobacco, alcohol, obesity, sedentary, poor diet and poor dental hygiene.

Chapter 6: Cardiovascular System: Blood

1. What is blood?Is a connective tissue known as the primary transportation medium in the body.

2. What is the composition of blood?As a connective tissue, it would be formed by specialized cells, ground substance and protein fibers.Specialized cells: Formed Elements (45%).Ground Substance: Plasma (< 55%).Protein Fibers: Albumins, Globulins and Fibrinogen (< 55%).

3. What are the functions of blood?Transport: Distributes oxygen from the lungs to the tissue cells; picks up nutrients from the digestive tract for delivery to the tissues; Transports

other wastes, besides hormones too.Defense: defends the body against pathogen invasion and blood lossRegulation: Helps regulate body temperature picking up heat and transporting it about the body.

4. Define: antibody, antigen anemia, hemolysis, immune system, hemophiliaAntibody: Is a protein that combines with and disables specific pathogens (made is response to the antigen).Antigen: Is any substance that is foreign to a person’s body.Anemia: Disease caused by the insufficient number of red blood cells or by the fact that the cells do not have enough hemoglobin. It provokes a

tired, run-down feeling.Hemolysis: Is the rupturing of red cells. Occurs in hemolytic anemia, when the rate of red blood cell destruction increases.Immune System: Consists of a variety of cells, tissues, and organs that defend the body against pathogens, cancer cells, and foreign proteins.Hemophilia: Is an inherited clothing disorder that causes a deficiency in a clothing factor.

5. What are the different types of formed elements present in blood?The red blood cells (erythrocytes; 99%), the white blood cells (leukocyte; < 0.5%) and the platelets (Thrombocyte; < 0.5%).

6. Know the characteristic features and functions of the three types of formed elements.Red Blood Cells: small and biconcave disks (donuts) that are produced in bone marrow, transports O2, and helps on transportations of CO2.White Blood Cells: Are larger the red blood cells, have a nucleus, lack hemoglobin, and are translucent unless stained. They are derived from stem cells in the red bone marrow and can be classified into the granular leukocytes and the agranular leukocytes. The difference between the two classifications consists in the fact that the granular type have noticeable cytoplasmic granules, which can be easily seen when the cells are stained and examined with a microscope, and the agranular type contain only sparse, fine granules, which are not easily viewed under a microscope.Platelets: Result from fragmentation of large cells (megakaryocytes), in the red bone marrow. They are involved in the process of blood clothing, or coagulation.

7. Why is the blood red in color?Because the most cells in the blood are the red blood cells (99%). These cells have a pigment called hemoglobin that make the blood red.

8. What is ABO blood type? Know the types of antigen and antibodies they produce.ABO blood type is a classification of the blood based on the presence or absence of two possible antigens (Type A and Type B antigen).

Blood Group Antigen Antibody II

A IAIA/ IAi

B IBIB/ IBi

AB IAIB

O ii

OBS: In a transplant, they want the antigen (red blood cells); AB is a universal recipient and O a universal donor.

9. What do you mean by Rh + and Rh - ? When is the Rh factor important?The designation of blood type usually also includes whether the person has or does not have the Rh factor on the red blood cell. The Rh -

individuals normally do not have antibodies to the Rh factor but they make them when exposed to the Rh factor (It is important in the relation mother x baby when she is pregnant).

Chapter 8: Digestive System

1. What are the main steps in the digestive process?Ingestion: Intake of food via the mouth.Digestion: Mechanically or chemically breaking down foods into their subunits.Movement: Food must be moved along the GI tract in order to fulfill all functions.Absorption: Movement of nutrients across the GI tract wall to be delivered to cells via the blood.Elimination: Removal of indigestible molecules.

2. What are the functions of the digestive system?Turning food into the energy (hydrolyze macromolecules to subunit molecules as monosaccharides, amino acids, fatty acids and glycerol) you need to survive and packaging the residue for waste disposal. The food also contains water, salts, vitamins, and minerals that help the body function normally.

3. What are the main layers of the GI track?Mucosa: Innermost layer that produces mucus to protect the lining and also produces digestive enzymes.Submucosa: Second layer of loose connective tissue that contains blood vessels, lymphatic vessels, and nervesMuscularis: Third layer made of two layers of smooth muscle that move food along the GI tract.Serosa: outer lining that is part of the peritoneum.

4. What is the pathway that food follows?Mouth – pharynx – esophagus – stomach – small intestine – large intestine – rectum – anus.

5. Explain the digestive process with the function of each organ. In the mouth, teeth chew the food, saliva contains salivary amylase for digesting starch, and the tongue forms a bolus for swallowing. Both the mouth and the nose lead into the pharynx. The pharynx opens into both the food passage (esophagus) and air passage (trachea, or

windpipe). During swallowing, the opening into the nose is blocked by the soft palate, and the epiglottis covers the trachea. Food enters the esophagus; and peristalsis begins. The esophagus moves food to the stomach. The stomach expands and stores food and also churns, mixing food with the acidic gastric juices. This juice contains pepsin, an enzyme that

digests protein. The duodenum of the small intestine receives bile from the liver and pancreatic juice from the pancreas. Bile emulsifies fat and readies it for

digestion by lipase. The pancreas produces enzymes that digest starch (pancreatic amylase), protein (trypsin), and fat (lipase). The intestinal enzymes finish the

process of chemical digestion. Small nutrient molecules are absorbed at the villi in the walls of the small intestine. The large intestine consists of the cecum; the colon (including the ascending, transverse, and descending colon); and the rectum, which ends at

the anus. The large intestine absorbs water, salts, and some vitamins; forms the feces; and carries out defecation. Disorders of the large intestine include diverticulosis, irritable bowel syndrome, inflammatory bowel disease, polyps, and cancer.

6. What is the importance of stomach, small intestine, large intestine?Large Intestine: The large intestine includes the cecum, colon, rectum, and anal canal. It is larger in diameter but shorter than the small intestine.

The cecum has a projection known as the appendix that may play a role in fighting infections. Its functions are: absorb water to prevent dehydration, absorb vitamins (B complex and K) produced by intestinal flora and form and rid the body of feces through the anus.

Small Intestine: The small intestine averages 6 m (18 ft) in length. Enzymes secreted by the pancreas into the small intestine digest carbohydrates, proteins, and fats. Bile is secreted by the gallbladder into the small intestine to emulsify fats. The absorption of digested food depends on the large surface area created by numerous villi (finger-like projections) and microvilli. Amino acids and sugars enter the capillaries while fatty acids and glycerol enter the lacteals (small lymph vessels).

Stomach: It functions to store food, start digestion of proteins, and control movement of chyme into the small intestine. The stomach is a J-shaped organ with a thick wall. There are three layers of muscle in the muscularis layer of the stomach wall to help in mechanical digestion and allow it to stretch. The mucosa layer has deep folds called rugae, and gastric pits that lead into gastric glands that secrete gastric juice. Gastric juice contains pepsin, an enzyme that breaks down proteins, plus HCl and mucus. HCl gives the stomach a pH of 2, which activates pepsin and helps kill bacteria found in food. A bacterium, Helicobacter pylori, lives in the mucus and can cause gastric ulcers. The stomach empties chyme into the small intestine after 2-6 hrs.

7. What are the accessory organs of the digestive system? Know their importance.Pancreas: The pancreas produces pancreatic juice, which contains digestive enzymes for carbohydrate, protein, and fat.

Liver: The liver produces bile, destroys old blood cells, detoxifies blood, stores iron, makes plasma proteins, stores glucose as glycogen, breaks down glycogen to glucose, produces urea, and helps regulate blood cholesterol levels.

Gallbladder: The gallbladder stores bile, produced by the liver. The secretions of digestive juices are controlled by the nervous system and by hormones.

8. What is the pH of the stomach? The pH of the stomach is 2 (acid).

9. How does the pH of the small intestine become basic?The small intestine has a slightly basic pH because pancreatic juice contains sodium bicarbonate (NaHCO3), which neutralizes chyme.

10. What is bolus and chyme?Bolus is the chewed food into a mass formed by the tongue in preparation for swallowing. Chyme is the thick soupy liquid of partially digested food that leaves the stomach.

11. Know the order for the major parts of the gastrointestinal tract.

12. How do we swallow food?Voluntary phase: In the beginning, food is being swallowed from the mouth into the pharynx. It is a voluntary act.Involuntary phase: Once the food is in the pharynx, swallowing becomes a reflex. The epiglottis covers the voice box to make sure food is routed

into the esophagus. Food moves down the esophagus through peristalsis (rhythmic contraction).

13. Know the different types of enzymes, their functions, site of production and action.

14. What is BMI? How do you measure BMI?BMI (Body Mass Index) is a general guide to estimate how much of a person’s weight is due to adipose tissue. It does not take into account gender, fitness, or bone structure. The BMI is measure by W/H².

Chapter 9: Respiratory System

1. What is the function of the respiratory system?The respiratory system is responsible for the process of ventilation (breathing), which includes inspiration and expiration. The organs of the respiratory system ensure that oxygen enters the body and carbon dioxide leaves the body

2. What are the components of the respiratory system and what their function?

The Upper Respiratory Tract

Nose/Nasal cavities: filters and warms the airPharynx: the opening into parallel air and food passageways. Blocks enter of food in the lower respiratory track.Glottis: Is the small opening between the vocal cords.Larynx: the voice box that houses the vocal cords.

The Lower Respiratory Tract

Trachea (windpipe): is lined with goblet cells and ciliated cells and is a passage of air to bronchi. The rings prevent a trachea to collapsing.Bronchus: along with the pulmonary arteries and veins, enter the lungs and branch into smaller bronchioles; is a passage of air to lungsBronchioles: passage of air to alveoli.Lungs: consist of the alveoli, air sacs surrounded by a capillary network; they carries out gas exchange.Diaphragm: skeletal muscle; functions in ventilation.

3. What is ventilation? Ventilation is another term for breathing that includes both inspiration and expiration.

4. What the Boyle’s Law say?

At a constant temperature, the pressure of a given quantity of gas is inversely proportional to its volume.

5. What happens during inspiration and expiration?Inspiration: An active process of inhalation that brings air into the lungs; The diaphragm (lowers) and intercostal muscles (breathing) contract;

The diaphragm flattens and the rib cage moves upward and outward.(contract too); Volume of the thoracic cavity and lungs increase; The air pressure within the lungs decreases; Air flows into the lungs.

Expiration: A typically passive process of exhalation that expels air from the lungs; The diaphragm and intercostal muscles relax; The diaphragm moves upward and becomes dome-shaped. The rib cage moves downward and inward (relaxes too); Volume of the thoracic cavity and lungs decreases; The air pressure within the lungs increases; Air flows out of the lungs.

6. How the breathing is controlled?Breathing is controlled by two ways: nervous control and chemical control.Nervous control: Respiratory control center in the brain (medulla oblongata) sends out nerve impulses to contract muscle for inspiration. Sudden

infant death syndrome (SIDS) is thought to occur when this center stops sending out nerve signals.Chemical control: Two sets of chemoreceptors sense the drop in pH: one set is in the brain and the other in the circulatory system. Both are

sensitive to carbon dioxide levels that change blood pH due to metabolism.

7. What are external and internal respiration?The internal and external respiration are types of respiration that depends on diffusion. Hemoglobin activity is essential to the transport of gases and, therefore, to external and internal respiration. In both respiration oxygen and carbon dioxide are exchanged and will diffuse from the area of higher to the area of lower partial pressure. Note that partial pressure is the amount of pressure each gas exerts (PCO2 or PO2).

External Respiration (gas exchange with atmosphere): Exchange of gases between the lung alveoli and the blood capillaries. PCO2 is higher in the lung capillaries than in the atmospheric air, thus CO2 diffuses out of the plasma into the lungs. The partial pressure pattern for O2 is just the opposite, so O2 diffuses from the red blood cells to the lungs. The enzyme carbonic anhydrase speeds the breakdown of carbonic acid (H2CO3) in red blood cells.

Internal Respiration (gas exchange with body tissues): The exchange of gases between the blood in the capillaries outside of the lungs and the tissue fluid. PO2 is higher in the capillaries than in the tissue fluid, thus O2 diffuses out of the blood into the tissues.

8. What do you mean by tidal volume, vital capacity, inspiratory reserve volume, expiratory reserve volume and residual volume?They are ways to measure respiratory volumes:Tidal volume: the small amount of air that normally enters and exits with each breath. Vital capacity: the amount of air that moves in plus the amount that moves out with maximum effort. Inspiratory reserve volume and the expiratory reserve volume: the difference between normal amounts and the maximum effort amounts of air

moved. Residual volume: the amount of air that stays in the lungs when we breathe.