Ch.27 Reproduction and Embryonic Development

WHAT IS A REPRODUCTIVE ANATOMY OF THE HUMAN FEMALE?
Ovaries contain follicles that nurture eggs and produce sex hormones. Oviducts convey eggs to the uterus where embryos develop. The uterus opens into the vagina through the cervix. THe vagina receives the penis during sexual intercourse and forms the birth canal.

WHAT IS A REPRODUCTIVE ANATOMY OF THE HUMAN MALE?
Testes produce sperm and male hormones. Epididymis stores sperm as they develop further and several glands contribute to semen, such as seminal vesicles, prostate, and bulbourethral. During ejaculation, sperm is expelled from the epididymis, and the seminal vesicles, prostate, and bulbourethral glands secrete into the urethra, then semen is formed and expelled from the penis. Sperm production is regulated by a negative feedback system of hormones, and it involves the hypothalamus, pituitary, and testes.

WHAT IS SPERMATOGENESIS?
The formation of sperm and egg requires meiosis. Spermatogenesis occurs in seminiferous tubules. IT has primary and secondary, and primary spermatocytes are formed by mitosis and they divide by meiosis I to produce secondary spermatocytes. Secondary spermatocytes divide by meiosis II to produce spermatids. Round spermatids differentiate into elongate sperm and mature sperm released into seminiferous tubule.


SUMMARY:
Some organisms can reproduce asexually and sexually. Some animals exhibit hermaphroditism. It is easier to find a mate for animals less mobile or solitary. Sperm may be transferred to the female by external fertilization or internal fertilization. Bot sexes in humans have a set of gonads where gametes are produced, ducts for gamete transport, and structures of copulation. Oogenesis begins before birth. Each month, about one primary oocyte resumes meiosis. A secondary oocyte arrested at metaphase of meiosis II is ovulated. Meiosis of the ovum is completed after fertilization. Ovarian and menstrual cycles occur about every 28 days. Hypothalamus signals the anterior pituitary to secrete FSH and LH. After ovulation, ovarian follicle becomes corpus luteum. Corpus luteum secretes estrogen and progesterone, which stimulate the endometrium to thicken, and prepare the uterus for implantation of the embryo. If egg is fertilized, embryo releases hormones that maintain the uterine lining, and menstruation does not occur. If egg is not fertilized, drop in LH shuts down corpus luteum and its hormones, menstruation is triggered, and hypothalamus and pituitary stimulate development of a new follicle. Sexual activity can transmit disease. Viral diseases can only be controlled, however bacterial diseases can often be cured. Embryonic development begins with fertilization. The union of sperm and egg to form a diploid zygote. Sperm are adapted to reach and fertilize an egg. Streamlined shape moves more easily through fluids. Many mitochondria provide ATP for tail movements. Cleavage is a rapid serious of cell divisions. It produces a ball of cells from the zygote. Gastrulation is when cells migrate. the basic body plan of three layers is established, ectoderm, endoderm, and mesoderm. Multiple processes give form to the developing animal. Tissues and organs develop by changes in cell shape, or cell migration, or programmed cell death. Induction is adjacent cells and cell layers, and also influence each other's differentiation via chemical signals. Human fertilization occurs in the oviduct. Cleavage produces a blastocyst. Placenta is close association of embryonic chorion, and mother's blood vessels. It is also a site of gas exchange, nutrient exchange, and waste exchange.

KEY TERMS:
- Asexual reproduction: one parent produces genetically identical offspring
- Sexual reproduction: fusion of gametes from two parents
- Hermaphroditism: one individual with male and female reproductive systems
- External fertilization: eggs and sperm are discharged near each other
- Internal fertilization: sperm is deposited in or near the female reproductive tract
- Ovaries: female reproductive organ
- Follicles: nurture eggs and produce sex hormones
- Spermatogenesis: occurs in seminiferous tubules
- Chiamydia: most common bacterial STD
- Contraception: the deliberate prevention of pregnancy

This diagram shows the structure of sperm. All the structures it has are made to be easy to get to the egg. The fastest and the best one usually gets to the egg to fertilize so that they can make a good offspring.
Streamlined shape moves easily through fluids. Many mitochondria provide ATP for tail movements. Head contains a haploid nucleus, and tipped with an acrosome containing penetrating enzymes.


http://www.youtube.com/watch?v=9MnQxiSJZ4Q
This video shows sperm fertilization.


5 FACTS:
1) Sexual reproduction results in the generation of genetically unique offspring.
2) The formation of sperm and egg requires meiosis.
3) Sexual activity can transmit diseases.
4) Contraception can prevent unwanted pregnancy.
5) Fertilization results in a zygote and triggers embryonic development.

Ch.26 Hormones and the Endocrine System

WHAT DISEASES CAN THYROID CAUSE?
The thyroid regulates development and metabolism. There are two big types of diseases that can be caused by the thyroid. Hyperthyroidism and hypothyroidism. Hyperthyroidism is when  too much T4 and T3 are in the blood and they lead to high blood pressure, loss of weight, overheating, and irritability. It can produce Graves disease. Hypothyroidism is when too little T4 and T3 are in the blood. It can lead to low blood pressure, overweight, often cold, and lethargy. They are the two opposite diseases.

WHAT IS DIABETES?
Diabetes is a common endocrine disorder. Diabetes mellitus results from a lack of insulin or a failure of cells to respond to it. It affects about 21 million Americans. There are two common types of diabetes mellitus. Type 1 is called insulin-dependent. It is an autoimmune disease and occurs when insulin producing cells are destroyed. Type 2 is called non-insulin dependent. It is deficiency of insulin and more commonly, reduced response to insulin. More than 90% of diabetics are type 2. It is associated with being overweight and underactive.

WHAT ARE THE STEROID SEX HORMONES?
The gonads secrete sex hormones. Steroid sex hormones include estrogens, progestins, and androgens. They are produced by the gonads in response to signals from hypothalamus and pituitary. Estrogens and progestins stimulate the development of female characteristics and they maintain the female reproductive system. Androgens such as testosterone trigger the development of male characteristics.

SUMMARY:
The endocrine system consists of all hormone, which is secreting cell and it works with nervous sytem to regulate body activities. The nervous system also communicates, regulates, and uses electrical signals via nerve cells. Nervous system reacts faster but endocrine system responses last longer. Hormone signaling involves three key events, which are reception, signal transduction, and response. Steroid hormones can diffuse through plasma membranes and they bind to a receptor protein in the cytoplasm or nucleus. The vertebrate endocrine system consists of more than a dozen glands and it secretes more than 50 hormones. The hypothalamus responds by sending out appropriate nervous or endocrine signals and it uses the pituitary gland to exert master control over the endocrine system. Pituitary glands consist of two parts. Posterior pituitary and anterior pituitary. Anterior pituitary is controlled by the hypothalamus.  Thyroid gland hormones are thyroxine and triiodothyronine. They regulate metabolism and development and it is a part of negative feedback. Blood calcium level is regulated by a tightly balanced antagonism between calcitonin from the thyroid and PTH from the parathyroid glands. Pancreatic hormones regulate blood glucose levels. Hormones from the adrenal glands help maintain homeostasis when the body is stressed. Nerve signals from the hypothalamus stimulate the adrenal medulla to secrete epinephrine, and norepinephrine. These hormones quickly trigger the fight-or-flight responses. ACTH from the pituitary causes the adrenal cortex to secrete glucocorticoids, and mineralocorticoids. Prolactin in humans stimulates mammary glands to grow and produce milk during late pregnancy. Sucking by a newborn stimulates further release of prolactin.


KEY TERMS:
- Hormones: chemical signal which cause specific changes in target cells
- Steroid hormones: non-polar lipids made from cholesterol
- Glands: specialized for hormone secretion only but some also do other jobs
- Hypothalamus: receives input from nerves about body conditions
- Posterior pituitary: stores and secretes oxytocin and ADH
- Anterior pituitary: synthesizes and secretes hormones that control the activity of other glands
- Releasing hormones: stimulate the anterior pituitary
- Inhibiting hormones: inhibit the anterior pituitary
- Pancreas: secretes two hormones that control blood glucose
- Insulin: signals cells to use and store glucose

This is a diagram of thymus gland.

Structure: the thymus lies beneath the sternum in the middle of the chest at the same level as the heart. It has a pyramidal shape and is divided into two lobes that separate at the mid-line of the body. It consists of two types of cells, lymphocytes and reticulin fibers, similar to other organs of the lymphatic system.

The thymus helps protect the body from foreign invaders, such as viruses and bacteria. However the thymus doesn’t filter lymphatic fluid to cleanse the body of toxins. Its primary function involves producing an array of highly specialized cells vital to the immune response. Its work involves thymosin, which promotes development of immune-system cells.

The thymus gland produces hormones called thymosins. Thymosins are involved in stimulating the growth of T lymphocytes, which help regulate the immune system. They also stimulate the production of other immune cells.


https://www.youtube.com/watch?feature=player_embedded&v=fPgQE9WgKpM

5 FACTS:
1) Hormones affect target cells by two main signaling mechanisms.
2) The vertebrate endocrine system consists of more than a dozen major glands.
3) The hypothalamus, which is closely tied to the pituitary, connects the nervous and endocrine systems.
4) Diabetes is a common endocrine disorder.
5) The adrenal glands mobilize responses to stress.

Ch.25 Control of Body Temperature and Water Balance

WHAT ARE REABSORPTION AND SECRETION?
Blood filtrate is refined to urine through reabsorption and secretion. High NaCl concentration in the medulla promotes reabsorption of water. Antidiuretic hormone regulates the amount of water excreted by the kidneys. Kidney dialysis can be a lifesaver by compensating.

WHAT IS THE RELATIONSHIP BETWEEN BEAR AND ITS CONCENTRATION?
Bears sleep a lot during winter, but bears do not hibernate. Instead, they become dormant. Their body temperature drops from 37C to about 31 to 34C. True hibernators may cool to 30C. Dormant bears are easily awakened and true hibernators are slower to awaken. That is the biggest difference between bears and true hibernators.

WHAT ARE EXAMPLES OF HOMEOSTASIS?
- Thermoregulation: the maintenance of internal temperature within narrow limits
The process by which animals maintain an internal temperature within a tolerable range. Ectothermic and endothermic animals are connected to them.

- Osmoregulation: the control of the gain and loss of water and solutes

Osmoconformers have the same internal solute concentration as seawater, and many marine invertebrates are osmoconformers. They control their solute concentrations.

- Excretion: the disposal of nitrogen-containing wastes

SUMMARY:
Heat exchange with the environment may occur by conduction, convection, radiation, and evaporation. Five general categories of adaptations promote thermoregulation. Increased metabolic heat production, humoral changes boost metabolic rate in birds and mammals, shivering, increased physical activity, and honeybees cluster and shiver. Circulatory adaptations increased or decreased blood flow to skin, large ears in elephants, and countercurrent heat exchange. Land animals gain water by drinking and eating, lose water by evaporation and waste disposal. and conserve water using. Nitrogenous wastes are toxic breakdown products of protein. Animals dispose of nitrogenous wastes in different ways. The excretory system expels wastes, regulates water balance and regulates ion balance. The key processes of the urinary system are filtration, reabsorption, secretion, and excretion. Filtration is when blood forces water and many small solutes into the nephron. Reabsorption is when valuable solutes are reclaimed from the filtrate. Secretion is excess H+ and toxins are added to the filtrate. Excretion is the final product, urine, is excreted. Reabsorption in the proximal and distal tubules removes nutrients, salt and water. pH is regulated by reabsorption of HCO3-, and secretion of H+.

KEY TERMS:
- Homeostasis: maintenance of steady internal conditions despite fluctuations in the external environment
- Thermoregulation: the maintenance of internal temperature within narrow limits
- Osmoregulation: the control of the gain and loss of water and solutes
- Excretion: the disposal of nitrogen-containing wastes
- Ectothermic: absorb heat from their surroundings
- Endothermic: derive body heat mainly from their metabolism
- Osmoconformers: have the same internal solute concentration as seawater
- Osmoregulators: control their solute concentrations
- Ammonia: poisonous, solube in water, easily disposed of by aquatic animals
- Nephrons: functional units of the kidneys, and extract a filtrate from the blood


http://www.youtube.com/watch?v=aQZaNXNroVY
This video talks about the urinary system and connection between the urinary system and the nephron.

5 FACTS:
1) An animal's regulation of body temperature helps maintain homeostasis.
2) Thermoregulation involves adaptations that balance heat gain and loss.
3) A variety of ways to dispose of nitrogenous wastes have evolved in animals.
4) The urinary system plays several major roles in homeostasis.
5) The key processes of the urinary system are filtration, reabsorption, secretion, and excretion.

Ch.24 The Immune System

WHAT ARE THE SIMILARITIES AND DIFFERENCES BETWEEN ACTIVE AND PASSIVE IMMUNITY?
Both are part of immune system. Both are artificial immunity, which is exposure to causative agent is not deliberate.
Active is active disease produces immunity. Passive is immunity passes from mother to fetus through placenta or from mother to child through mother’s milk.
Artificial immunity is exposure to causative agent is deliberate. Active is vaccination results in immunity. Passive is protective material developed in another individual’s immune system and given to previously non-immune individual. Active occurs when an individual’s own immune system responds to a harmful agent, regardless of whther that agent was naturally or artificially encountered. Passive immunity results when immunity to a disease that has developed in another individual or animal is transferred to an individual who was not previously immune. Active generally lasts longer than passive.

WHAT ARE PHAGOCYTES?
Ingest and destroy foreign cells or other harmful substances via phagocytosis. Neutrophils, monocytes, and macrophages are the examples.

WHAT ARE T CELLS AND B CELLS?
T cells: Produce cell-mediated immunity; kill invading cells by releasing a substance that poisons cells and also by releasing chemicals that attract and activate macrophages to kill cells by phagocytosis.
B cells: Indirectly, B cells produce humoral immunity; activated B cells develop into plasma cells; plasma cells secrete antibodies into the blood; circulating antibodies produce humoral immunity.

SUMMARY:
Invertebrates have only innate immunity, while vertebrates have innate and acquired immunity. The inflammatory response mobilizes innate defenses. Tissue damage triggers the inflammatory response. It can disinfect tissues and limit further infection. Lymphatic vessels collect fluid from body tissues, and return it as lymph to the blood. Lymph organs are packed with WBCs that fight infections. Our immune system responds to foreign molecules called antigens. The acquired immune system reacts to antigens and remembers an invader. Infection or vaccination triggers active immunity. We can temporarily acquire passive immunity by receiving premade antibodies. Two kinds of lymphocytes carry out the immune response, B cells and T cells. When an antigen enters the body, it activates only a small subset of lymphocytes. Those with complementary receptors. The selected lymphocyte cells multiply into clones of short-lived effector cells. Primary response occurs upon first exposure to an antigen and it is slower than the secondary response. The secondary immune response occurs upon second exposure to an antigen and it is faster and stronger than the primary immune response. In the cell-mediated immune response, an antigen presenting cell displays a foreign antigen and one of the body's own self proteins to a helper T cell. The helper T cell's receptors recognize the self-nonself complexes and the interaction activates the helper T cells. Cytotoxic T cells are the only T cells that kill infected cells. They bind to infected body cells to destroy them. AIDS results from infection by HIV. They attack helper T cells, opening the way for opportunistic infection. HIV mutates faster than any pathogen ever studied.



KEY TERMS:
- Innate defenses: first line of defense that can be found in all animals
- Interferons are proteins produced by virus-infected cells
- Lymphatic system: network of lymphatic vessels and organs
- Antigenic determinants: specific regions on an antigen to which antibodies bind
- Primary immune response: produces effector cells
- Secondary immune response: memory cells are activated by a second exposure to the same antigen
- Antibodies: secreted by plasma B cells into the blood and lymph
- mAb: produced by fusing and its name means all antibody-producing cells come from one cell
- Helper T cells: stimulate the humoral response
- Cytotoxic T cells: primarily responsible for the cell-mediated immune response

This is a diagram of HIV virus. HIV is a virus that is transmitted from person to person through the exchange of body fluids such as blood, semen, breast milk and vaginal secretions. Sexual contact is the most common way to spread HIV AIDS, but it can also be transmitted by sharing needles when injecting drugs, or during childbirth and breastfeeding. As HIV AIDS reproduces, it damages the body's immune system and the body becomes susceptible to illness and infection. There is no known cure for HIV infection.




http://www.youtube.com/watch?v=68I7JlVhuhY

This video talks about connection between HIV and AIDS. Especially when HIV becomes AIDS.




5 FACTS:
1) Both invertebrates and vertebrates have innate defenses against infection.
2) The acquired immune response counters specific invaders.
3) Clonal selection musters defensive forces against specific antigens.
4) Antibodies promote antigen elimination through several mechanisms.
5) Helper T cells stimulate the humoral and cell-madiated immune responses

Ch.23 Circulation

WHAT IS A HEART ATTACK?
A heart attack is when cardiac muscle gets damaged typically from a blocked coronary artery. Atherosclerosis is plaques develop inside inner walls of blood vessels. Plaques narrow blood vessels. Blood flow is reduced.

WHAT ARE THE DIFFERENCES AND SIMILARITIES BETWEEN ARTERIES AND VEINS?
Arteries carry blood away from the heart. Aorta is the largest arteries. Veins carry blood towards the heart. Superior, inferior vena cave is the largest veins. They both lined by single layer of epithelial cells. The smooth muscle in walls can reduce blood flow. Elastic ibers permit recoil after stretching. Veins have one-way valves that restrict backward flow.

HOW DOES BLOOD TRAVEL AGAINST GRAVITY?
Blood travels by pressure from muscle contractions between two muscles and between muscles and bone or skin. Also when veins are squeezed, blood can travel against gravity. One other way of blood traveling against gravity is one way valves limit blood flow to one direction, towards heart.

SUMMARY:
For circulatory system, all cells need nutrients, gas exchange which was discussed about in last blog, and removal of wastes. Diffusion alone is inadequate for large and complex bodies. Arthropods and many molluscs use open circulatory systems while other animals use closed circulatory system. The mamalian heart has two thin-walled atria and thick-walled ventricles. The pacemaker sets the rate of heart contractions and it generates electrical signals in atria. Heart attack is damage to cardiac muscle typically from a blocked coronary artery. Stroke is death of brain tissue from blocked arteries in the head. Capillaries have thin walls and are narrow and increase surface area for gas and fluid exchange. Veins and arteries are the main types of blood that go through the heart. Blood pressure is the force blood exerts on vessel walls. It depends on cardiac output and resistance of vessels. It decreases as blood moves away from heart. Hypertension is a serious cardiovascular problem. It can cause heart to work harder, weakening over time, increased plaque formation from tiny ruptures, and increased of blood clot formation. Those conditions can cause heart attacks, strokes, and kidney failure.
Blood consists of red and white blood cells suspended in plasma. Plasma is the fluid that contains various inorganic ions, proteins and nutrients, wastes, gases, and hormones. RBCs transport oxygen bound to hemoglobin. WBCs function inside and outside the circulatory system. They fight infections and cancer. The blood-clotting process is platelets adhere to exposed connective tissue, platelets form a plug, and a fibrin clot traps blood cells. Stem cells divide in bone marrow to produce all the types of blood cells throughout life and they are used to treat some blood disorders.



KEY TERMS:
- Open circulatory systems: heart pumps blood through open-ended vessels
- Closed circulatory system: heart pumps blood through arteries to capillaries
- Double circulation: separate pulmonary and systemic circuits
- Diastole: blood flows from veins into heart chambers
- Systole: blood flows from atria into ventricles
- Cardiac output: amount of blood/minute pumped into systemic circuit
- Heart rate: number of beats/minute
- Heart valves: prevent the back flow of blood
- Heart murmur: a defect in one or more heart valves
- The AV node: relays these signals to the ventricles

This is a diagram of inside a red blood cell and shows the structure of hemoglobin. Hemoglobin has red pigment, which makes the blood red. Hemoglobin carries oxygen throughout the body and it contains oxygen molecule. Red blood cell is made of hemoglobin.

http://www.youtube.com/watch?v=WXOBJEXxNEo

This video talks about the oxygen transport in the body.

5 FACTS:
1) Circulatory systems facilitate exchange with all body tissues.
2) Blood flow through the double circulatory system of humans.
3) The pacemaker sets the tempo of the heartbeat.
4) Smooth muscle controls the distribution of blood.
5) Capillaries allow the transfer of substances through their walls.

Ch.22 Gas Exchange

HOW ARE GILLS RELATED TO GAS EXCHANGE IN AQUATIC ENVIRONMENTS?
Gills are adapted for gas exchange in aquatic environments. In a fish, gas exchange is enhanced by ventilation of the gills (moving water past the gills), and countercurrent flow of water and blood. Cold water holds more oxygen than warm water. Fresh water holds more oxygen than salt water. And turbulent water holds more oxygen than still water. Therefore, fish go to whichever that is the easiest for them to breath in the oxygen.

WHAT ARE TETRAPODS?
Tetrapods seem to have evolved in shallow water. This is because fossil fish with legs had lungs and gills. Legs may have helped them lift up to gulp air. The fossil fish illustrates these air-breathing adaptations. The first tetrapods on land diverged into three major lineages. Amphibians use small lungs and their body surfaces. Nonbird reptiles have lower metabolic rates and simpler lungs. Birds and mammals have higher metabolic rates and more complex lungs.

WHAT IS ALVEOLI?
Alveoli are well adapted for gas exchange. High surface area of capillaries and high surface are of alveoli. In alveoli, oxygen diffuses into the blood, and carbon dioxide diffuses out of the blood. Basically, It is the place in the body where carbon dioxide and oxygen change places in the lungs. It is the place in the body where carbon dioxide and oxygen changes in the lungs.

SUMMARY:
The process of gas exchange is the interchange of oxygen and carbon dioxide between an organism and its environment. Three phases of gas exchange are breathing, transporting of oxygen and carbon dioxide in blood, and body tissues take up oxygen and release carbon dioxide. Cellular respiration requires a continuous supply of oxygen and the disposal of carbon dioxide. Respiratory surfaces must be thing and moist for diffusion of O2 and CO2.  Compared to water, using air to breathe has two big advantages; air contains higher concentrations of O2. And air is lighter and easier to move. For humans to breathe, from the nasal cavity air next passes to the pharynx, past the vocal cords, into the trachea, into the paired bronchi, into bronchioles, and finally to the avaoli. Smoking is very bad for lungs and the respiratory system. It can cause lung cancer, heart disease, and emphysema. Breathing is the alternate inhalation and exhalation of air. Inhalation occurs when the rib cage expands, or when the diaphragm moves downward. Exhalation occurs when the rib cage contracts, or when the diaphragm moves upward. Not all air is expelled during exhalation. One-way flow of air in birds reduces dead air and increases their ability to obtain oxygen. Breathing is usually under automatic control. The heart pumps blood to two regions, the right side pumps oxygen poor blood to the lungs, and the left side pumps oxygen rich blood to the body. In the lungs, blood picks up O2 and drops off CO2. In the body tissues, blood drops off O2 and picks up CO2. Most CO2 in the blood is transported as bicarbonate ions in the plasma. In the placenta, capillaries of maternal blood and fetal blood run next to each other. Fetal hemoglobin attracts O2 more strongly than adult hemoglobin. Thus, fetal blood takes oxygen from maternal blood. At birth, CO2 in fetal blood increases. Breathing control centers initiate breathing.

KEY TERMS:
- Gills: specialized body parts that promote gas exchange in fish and amphibians
- Tracheal systems: specialized body parts that promote gas exchange in arthropods
- Lungs: in tetrapods that live on land such as amphibians, reptiles, birds, and mammals
- Trachea: held open by cartilage rings
- Alveoli: grapelike clusters of air sacs, where gas exchange occurs
- Mucus: protection of lungs, which can be damaged by smoking
- Breathing control centers: in the brain sense and respond to CO2 levels in the blood
- Hemoglobin: transports oxygen, buffers blood, and transports CO2
- Human fetus: instead of breathing with lungs, exchanges gases with maternal blood in the placenta
- Placenta: an organ attached to the lining of your womb during pregnancy

This diagram shows where the blood from comes from, and goes to. Right Heart receives blood from the body and pumps it through artery to the lungs where it picks up oxygen. •Left Heart receives oxygen-rich blood from the lungs and pumps it through the aorta to the body.

http://www.youtube.com/watch?v=bwXvqSqAgKc

This video talks briefly about the respiratory system.


5 Facts:
1) Animals exchange O2 and CO2 across moist body surfaces.
2) In the human respiratory system, branching tubes convey air to lungs located in the chest cavity.
3) Without healthy cilia, smokers must cough to clear dirty mucus from the trachea.
4) Negative pressure breathing ventilates our lungs.
5) A drop in blood pH increases the rate and depth of breathing.

Ch.21 Nutrition and Digestion

WHAT IS ACID PEPSINOGEN AND HCl?

Stomach stores food and breaks it down with acid and enzymes. In this case, Acid is pH 2, and parietal cells secrete hydrogen and chloride ions, which combine to make HCl. Acid kills bacteria in food and breaks apart cells in food. Pepsinogen and HCl produce pepsin. Pepsin production activates more pepsinogen production, which is a positive feedback for digestion. Pepsin begins the chemical digestion of proteins. Acidic gastric juices mix with food to produce acid chyme.

WHAT ARE THE FUNCTIONS OF THE LIVER?

The liver performs many functions. One of the main function of liver is processing nutrient laden blood from the intestines. Blood from the digestive tract drains to the liver. Also other functions are glucose in blood is converted to glycogen and stored in the liver. Liver synthesizes many proteins including blood clotting proteins and lipoproteins that transport fats and cholesterol. Liver also changes toxins to less toxic forms and it produces bile.

WHAT IS THE HUMAN HEALTH PROBLEM OF OBESITY?

Obesity may reflect our evolutionary past. Overnourishment is consuming more food energy than is needed. World health organization recognizes obesity as a major global health problem. Of all the people in the United States, 30% are obese, 35% are overweight, and 155 of children and adolescents are overweight. Obesity leads to diabetes, cancer, and cardiovascular disease.

SUMMARY:

Most animals are herbivores, carnivores, or omnivores. Animals obtain and ingest their food in different ways, suspension feeding, substance feeding, fluid feeding, or bulk feeding. And food is processed ingestion first, digestion second, absorption third, and elimination last. Sponges digest food in vacuoles, while most animals digest food in compartments. Cnidarians and flatworms have a gastrovascular cavity with a single opening, the mouth. Teeth break up food, saliva moistens it, and tongue tastes, shapes the bolus of food, and moves it toward the pharynx. The Heimlich maneuver can dislodge food from the pharynx or trachea during choking. Brain damage will occur within minutes if no airway is open. Nutrients pass across the epithelium and into blood. Blood flows to the liver where nutrients are processed and stored. Blood from the digestive tract drains to the liver. The length of the digestive tract often correlates with diet. For example herbivores and omnivores have relatively longer digestive tracts than carnivores. Many hervivores have specializations of the intestine that promote the growth of cellulose.

Nutrients are oxidized inside cells to make ATP. ATP is the main energy currency in a cell. Excess energy can be stored as glycogen or fat. The eight essential amino acids can obrained from animal protein, and the proper combination of plant foods. The essential proteins are the ones that animals cannot produce. Food labels indicate serving size, calories per serving, amounts of selected nutrients per serving and as a percentage of daily value, and recommendations for daily limits of selected nutrients.

KEY TERMS:

- Herbivores: plant eaters

- Carnivores: meat eaters

- Omnivores: eating both plants and other animals

- Pyloric sphincter: regulates the passage of food from the stomach to the small intestine

- Diarrhea: occurs when too little water is reclaimed

- Constipation: occurs when too much water is reclaimed

- Colon bacteria: production of biotin, vitamin K, B vitamins

- Appendix: located near the small intestine and colon and makes a minor contribution to immunity

- BMR: the energy a resting animal requires each day

- Metabolic rate: the BMR plus the energy needed for physical activity

Valine is needed for muscle metabolism, tissue repair, and for the maintenance of proper nitrogen balance in the body. Valine is found in high concentration in the muscle tissue. It can be used as an energy source by muscle tissue. It may be helpful in treating livere and gallbladder disorders, and it is good for correcting the type of severe amino acid deficiencies that can be caused by drug addiction. Dietary sources of valine include dairy products, grain, meat, mushrooms, peanuts, and soy proteins.

5 FACTS:

1) Mechanical digestion breaks food down into smaller pieces.

2) Chemical digestion breaks down large organic molecules into their components.

3) Most animals have an alimentary canal with mouth, anus, and specialized regions.

4) Enzymes from cells of the intestine continue digestion.

5) Small intestine is the major organ of chemical digestion and nutrient absorption.