CHAPTER 12 – THE HUMAN BODY



CHAPTER 12 – THE HUMAN BODY

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Note: It would be useful for the teacher to have access to a butchery during the teaching of this chapter. The organs of a goat, sheep or pig are quite similar to the corresponding human organs and are very suitable for demonstration. If organs from these or similar animals are not available, those of a small mammal such as a rabbit or of a domestic fowl (chicken) could be used as alternatives. It is not necessary to have such materials available for every module, but it is desirable for students to see real organs at some time.

12.1 THE SYSTEMS OF THE HUMAN BODY

Aims:

• To make students aware of the systems of the human body and their general functions.

• To remind students about cells (studied in Module 5.3 & 5.4) and introduce them to the notions of tissues and organs.

• To review the general features and functions of the circulatory system (studied in Module 8.2).

Activities:

• Introduce the idea of the systems of the human body and the organs that comprise them. Encourage students to discuss what they already know or believe they know. Throughout this topic, encourage students to refer to their own bodies as examples. Focus this initial discussion on the more obvious systems such as skeletal, muscular, digestive and respiratory.

• Review previous work on cells (Modules 5.3 – 5.4) focussing on animal cells and growth in multi-cellular organisms. Then introduce the idea that organs are made of tissues, each of which is composed of millions of identical or similar cells. Use samples of red meat (muscle and fat), chicken thighs (muscle, bone, skin and connective tissues) to make sure they are familiar with examples of a few tissues. A heart with blood vessels attached would be useful for revising the circulatory system. Models or charts of the human body would also be useful if available.

• Review previous work on the circulatory system (Module 8.2). Focus on the general functions of the system and do not allow students to become distracted or confused by too much detail!

• Encourage students to try the questions at the end of the module. Follow up by discussing their attempts. Make sure they are aware of, and understand, the correct answers.

Answers:

• Q1. (i) Cells are the tiny ‘building blocks’ from which all living things are made. There are many different kinds of cell, but all cells are surrounded by a cell membrane. All cells contain a living jelly called cytoplasm and a control centre called the nucleus. (ii) Tissues are the materials that organs are made of. Each tissue is made of millions of cells all of the same kind, or of a few similar kinds. (iii) Organs are the working parts of a living organism. Each organ has a specific function.

• Q2. A system of the human body consists of a group of organs that work together to perform a general function such as movement, respiration or transport of materials around the body. The systems of the body work closely together and depend on one another – they are inter-dependent, not independent!

• Q3. Sensitivity means responding to conditions or situations – for example moving out of the sun if you are too hot, or ducking if something is thrown at you! Co-ordination means making different systems or organs work together. For example, to catch something that is thrown at you, you have to coordinate the movement of your hands with what your sight is telling you about the position of the object thrown!

12.2 THE RESPIRATORY SYSTEM

Aims:

• To provide students with basic information about, and understanding of, the respiratory system, how it works and how it contributes to the needs of the body.

Activities:

• Use an introductory lesson to review thoroughly with students, Module 6.11 about breathing and respiration, including the respiration equation. Emphasise the differences between inhaled and exhaled air and demonstrate or discuss the activities described in that module. Review also, the parts of Modules 8.2 and 8.4 that deal with the circulation of the blood to the lungs and to the rest of the body; also the functions of the red blood cells and the plasma in carrying oxygen, carbon dioxide and water.

• Emphasise the fundamental importance of respiration in the cells to the functioning of the human body.

• Discuss with students the information provided in the textbook regarding the structure and functioning of the respiratory system. If possible show them the lungs of a sheep, goat or pig; it may be possible to inflate the lungs by blowing down a tube inserted in the trachea. Make sure that students can identify the positions of the lungs and diaphragm in their own bodies and refer to any additional models and diagrams that may be available.

• Encourage students to try the questions at the end of the module. Follow up by discussing their attempts. Make sure they are aware of, and understand, the correct answers.

Answers:

• Q1. Compared to inhaled (normal) air, exhaled air contains less oxygen, more carbon dioxide and more water vapour. It is also warmer! (See Module 6.11).

• Q2. Mucus is a sticky liquid that cleans the air passing through the trachea by trapping particles of dust and dirt. Cilia are like tiny hairs on the walls of the trachea that push the mucus towards the mouth where it can be swallowed. The mucus may also be coughed up. (You should take the opportunity to warn students that spitting spreads disease and should be avoided!).

• Q3. When I run, my muscles are working hard. They need more energy than usual from respiration, so my lungs must work faster to send more oxygen. A molecule of oxygen is absorbed by a red blood cell, in a tiny sack called an alveolus in my lung. The molecule of oxygen is carried by the red cell along a vein to the left side of my heart. The heart pumps it out again through a huge artery. The artery has many branches and the molecule of oxygen eventually reaches my leg and goes along a tiny capillary leading to my leg muscle. It is taken by a muscle cell and used for respiration. Respiration gives the muscle the energy it needs to help me run. During respiration, the molecule of oxygen becomes part of a molecule of carbon dioxide. The carbon dioxide is absorbed by the plasma in the blood which carries it along a tiny capillary, into a vein, and back to the right side of the heart. Finally, the right side of my heart pumps the blood containing the carbon dioxide back to the lungs were it is released into an alveolus and I breathe it out. So the oxygen molecule, which is now part of a carbon dioxide molecule, returns to the air again. (See Modules 8.2 to 8.4 for details of the blood and its circulation).

12.3 THE DIGESTIVE SYSTEM

Aims:

• To make students aware of the four food groups that constitute the bulk of what we eat, and of digestion as the process of breaking down these for distribution to meet the needs of all parts of our bodies.

• To provide students with basic information about, and understanding of, the digestive system, how it works, and how it contributes to the needs of the body.

Activities:

• Start off by discussing what students eat. Have local foods to show them and identify examples of good sources for each of the four bulk food groups. (Nutrition and the balanced diet will be studied later in Chapter 17. At this stage we are interested only in a much broader picture).

• Emphasise the fundamental nature of digestion as a process of breaking down foods into simpler substances that our bodies can absorb, our blood transport, and our cells use.

• Discuss with students the information provided in the textbook regarding the structure and functioning of the digestive system. Refer wherever possible to the students’ own bodies and experiences as examples, and make sure that they can identify the positions of the gullet, stomach and intestines in their own bodies. If convenient, show them the guts of a sheep, goat or pig and make use of any models/diagrams that may be available. Peristalsis can be demonstrated by forcing a pea or similar object through a rubber or plastic tube by squeezing it along. Focus on helping students to understand the basic ideas involved and do not confuse them with unnecessary details (unless required by your local syllabus).

• Encourage students to try the questions at the end of the module. Follow up by discussing their attempts. Make sure they are aware of, and understand, the correct answers.

Answers:

• Q1. (i) A gland is an organ that produces and secretes (delivers) one or more substances needed by the body for specific purposes. (ii) An enzyme is a substance that assists in the chemical break-down of food during digestion. (Enzymes also have other roles but this is an adequate definition at this stage). (iii) Peristalsis is the process used to move food through the gullet and intestines. It involves the muscles in the tube squeezing just behind the food and thus forcing it along.

• Q2. The intestine digests food with the help of enzymes from the pancreas and bile from the liver. These all enter the duodenum, which is the first part of the small intestine. The enzymes help to turn carbohydrates into glucose and proteins into amino acids. Fats are emulsified by the bile and then turned into fatty acids by the enzymes. The digested food is absorbed through the villi on the walls of the small intestine and goes into the blood capillaries inside the villi. Water is absorbed through the walls of the large intestine. A feature of the small intestine that helps absorption is the villi that cover its walls. These greatly increase the surface area for absorption. Another feature is the great length of the intestine. This increases both the surface area and the time available for absorption.

• Q3. Glucose is the soluble sugar used for respiration. It comes from the digestion of carbohydrates. Digestion of carbohydrates starts in the mouth where an enzyme in saliva starts converting starch to sugar. In the small intestine, more enzymes convert remaining carbohydrates into glucose.

12.4 THE LIVER, THE LYMPHATIC SYSTEM AND THE SPLEEN

Aims:

• To make students aware of the position, size and importance of the kidney and spleen, and to inform them about some of their functions.

• To make students aware of the lymphatic system as a drainage system that works throughout the body in support of the circulatory system, and to understand how it functions.

Activities:

• Help students to identify the positions of the kidney and spleen in their bodies and discuss what they know about their functions. Discuss the information provided in the textbook and if convenient show them a liver and a spleen from the butchery. (They should be aware of the importance and of these organs, but it is not necessary for most of them to memorise detailed lists of functions).

• Discuss with students the information provided in the textbook regarding the structure and functioning of the lymphatic system. If convenient, show them a lymph vessel from the butchery. Refer wherever possible to the students’ own bodies and experiences as examples.

• Encourage students to try the questions at the end of the module. Follow up by discussing their attempts. Make sure they are aware of, and understand, the correct answers.

Answers:

• Q1. The liver is a big organ because it has to perform many complex functions (as listed by the dot points in the textbook).

• Q2. (i) Plasma is the clear, pale yellowish, liquid part of the blood. (ii) Lymph is the liquid that flows in the lymph vessels. It comes from the plasma and has a similar composition. (iii) Lymphocytes are white blood cells that destroy foreign bacteria and viruses. (iv) Lymph nodes are small, roundish organs where several lymph vessels come together. They contain lymphocytes and are situated especially in the neck, arm pits, groin and trunk.

• Q3. Tissue fluids are released into the tissues and drain into the lymph vessels all over the body, all the time. Because there is no pump in the lymphatic system, movement of the lymph along the lymph vessels depends on general muscular activity. If you are sitting and not moving around, the leg muscles are not active and the lymph vessels in the feet fill up. When more tissue fluid is released in the feet, it has nowhere to go and the feet start to swell! (Passengers on long international plane flights often find their feet swelling. To avoid this, they should get up and walk around from time to time).

12.5 THE EXCRETORY SYSTEM

Aims:

• To make students aware of the body’s need for an excretory system to remove the waste products of bodily processes, including the destruction of dead cells.

• To inform students about the excretory functions of the lungs, liver and skin.

• To provide students with basic information about the urinary system and its role in excretion.

Activities:

• Discuss the importance of the proper disposal of waste materials in everyday life. This can lead on to discussing the same issue in regard to the human body and identifying of some of the main wastes to be disposed of. Emphasise the breakdown of dead cells as a process producing waste materials.

• Discuss with students the information provided in the textbook regarding excretion, and the structure and functioning of the urinary system. If convenient, show students a kidneys and a bladder from the butchery. Refer wherever appropriate to the students’ own bodies and experiences as examples, and make sure that they can identify the positions of the kidneys and bladder in their own bodies. Use any additional models and diagrams that may be available.

• Encourage students to try the questions at the end of the module. Follow up by discussing their attempts. Make sure they are aware of, and understand, the correct answers.

Answers:

• Q1. Excretion is necessary to remove waste products from the body. If they were not removed they would accumulate and stop the body working properly (that is to say, they would poison it). (i) Carbon dioxide is carried away from the tissues by the blood and excreted in the lungs. (ii) Nitrogenous wastes are processed in the liver to form urea. The urea is carried by the blood to the kidneys where it is excreted in the urine.

• Q2. (i) The kidneys remove water, urea, salt and other waste products from the blood and excrete it as urine into the ureters. (ii) The ureters carry urine to the bladder. (iii) The bladder stores urine. (iv) The sphincter muscle controls the exit from the bladder into the urethra. (v) The urethra carries urine from the bladder to the outside of the body.

12.6 THE SKELETAL-MUSCULAR SYSTEM

Aims:

• To inform students about the structure and functions of the skeletal and muscular systems.

Activities:

• Try to find any available animal bones, including vertebrae, to take to the class. If possible cut open a large bone such as a femur to show the marrow and spongy bone inside.

• Discuss with students the information provided in the textbook regarding skeletal-muscular system. Refer wherever appropriate to the students’ own bodies and experiences as examples, and make sure that they can identify the positions of the more important bones and muscles in their own bodies. Show them any bones you have been able to bring to the class, stressing the importance of the backbone and its flexibility. Use any additional models and diagrams that may be available.

• Encourage students to try the questions at the end of the module. Follow up by discussing their attempts. Make sure they are aware of, and understand, the correct answers. The answer to Q3 raises an important issue and should be discussed thoroughly.

Answers:

• Q1. (i) The heart is protected by the ribs. (ii) The spinal chord is protected by the spinal (or vertebral column). (iii) The brain is protected by the skull. (iv) The lungs are protected by the ribs.

• Q2. Cartilage is a tough, flexible material . It is found between the bones in joints and in the vertebral column. It allows the bones to move without wearing against one another.

• Q3. The triceps muscle pulls a bent elbow straight. (Muscles are no good at pushing – they can only pull, so all joints need a muscle on each side, one to bend the joint and one to straighten it).

• Q4. Since we gain about 6 times the distance moved, we lose 6 times the force. Therefore our biceps have to use a force of about 60 kg (or 600N) to lift 10 kg. (Review Module 10.9 if necessary!).

12.7 THE SENSORY-NERVOUS SYSTEM

Aims:

• To make students aware of our sensory organs and their role in keeping us informed about our surroundings.

• To provide students with basic information about structure and functions of the nervous system and its roles in (i) voluntary and reflex actions, and (ii) coordinating the actions of the human body.

• To make students aware of the human brain as (i) an array of interconnected nerve cells, and (ii) a super-computer that gives us unique abilities as regards such things as awareness, language, thought and imagination.

Activities:

• Remind students about their study of the eye and the ear (Modules 7.12 & 15) and discuss the other senses. Those located in the skin are discussed in a later module so a brief mention will be sufficient.

• Discuss with students the information provided in the textbook regarding the structure of the nervous system. Identify the central nervous system (brain and spinal chord) and stress that they are well protected by bones. Show them a vertebra from an animal and point out the hole for the spinal chord. Let them feel the vertebrae in their own backbones, especially at the back of the neck, and stress that the spinal chord is like a long extension of the brain.

• Discuss with students the information provided in the textbook regarding the functioning of the sensory-nervous system Refer wherever possible to the students’ experiences as examples. The eye of a sheep, goat or pig with the optical nerve attached might provide a useful example.

• Encourage students to try the questions at the end of the module. Follow up by discussing their attempts and make sure they are aware of, and understand, the correct answers.

Answers:

• Q1. (i) Motor nerve cells are found mainly in the central nervous system. They receive inputs through dendrites and they have long axons that transmit these inputs as electrical impulses to muscles or glands throughout the body. (ii) Sensory nerve cells are found throughout the body in the sense organs, including those in the skin and internal organs. They have long dendrons that transmit electrical impulses from the sense organs to the central nervous system. (iii) Multi-polar nerve cells are found in the brain. Each cell can link with many others through their dendrites.

• Q2. First my brain tells my ears to listen to the question. The sound vibrations in the air enter my ear and pass on to the cochlea in my inner ear. The sensory nerve cells in the cochlea send impulses to my brain through the dendrons in my auditory nerve. My brain interprets these impulses as words and tries to understand the problem and work out the answer. Then my brain sends impulses through the axons of my motor nerve cells to my speaking muscles and I say the answer (or maybe to my writing muscles and I write the answer).

12.8 THE ENDOCRINE SYSTEM

Aims:

• To inform students about the positions and main functions of the endocrine glands.

Activities:

• Discuss with students the information provided in the textbook regarding endocrine system. Refer wherever appropriate to the students’ own bodies and experiences as examples and, if convenient, show them any endocrine glands that you may have been able to obtain from the butchery. Make sure that they can identify the positions of the glands in their own bodies. Use any additional models and diagrams that may be available.

• Encourage students to try the questions at the end of the module. Follow up by discussing their attempts. Make sure they are aware of, and understand, the correct answers. You could follow up Q3 by discussing the issue of responsibility. (For example, if feelings of aggression are influenced by hormones, does that mean we are not to blame if we behave violently?)

Answers:

• Q1. The pituitary gland is called the master gland because it switches on and/or controls the activity of most of the other endocrine glands.

• Q2. (i) Gigantism is caused by too much human growth hormone. (ii) Diabetes is caused by too little insulin from the pancreas.

• Q3. The dog on the left is very aggressive. His testes are probably releasing testosterone into his blood. The dog on the right is very frightened. His adrenal glands are releasing lots of adrenaline into his blood very quickly. The adrenaline makes his eyes open wide, his heart beat quickly and his rate of breathing increase. His blood is diverted to the muscles in his legs to help him run fast!

12.9 THE SKIN

Aims:

• To inform students about nature of the epidermis and dermis, and the roles of the skin as regards sensing our surroundings and controlling our temperature.

Activities:

• Discuss with students the information provided in the textbook regarding the skin. Refer wherever appropriate to the students’ own bodies and experiences to exemplify ideas. Depending on the climate, get students to help you demonstrate how the skin responds to heat and/or cold. (They will understand the role of dilating or constricting capillaries much better if they actually observe it). Use any additional models and diagrams that may be available.

• Encourage students to try the questions at the end of the module. Follow up by discussing their attempts. Make sure they are aware of, and understand, the correct answers.

Answers:

• Q1. (i) The epidermis is the outer layer of the skin. It is composed of living and dividing cells covered by a tough layer of dead cells. It also contains pigments. (ii) The dermis is the thicker, second layer of the skin. It contains various organs including capillaries, nerves, sense organs and sweat glands. (iii) Capillaries are tiny blood vessels that deliver food and oxygen to the tissues and carry away wastes.

• Q2. The fat cells under the skin help to insulate and protect the body, and provide a store of energy.

• Q3. The skin responds to cold by constricting the capillaries and reducing sweating to minimise heat loss; it main also raise the hairs to trap more insulating air.

• Q4. The hair muscles makes your hair stand on end. (The hair muscle may triggered by the hormone adrenaline when you are alarmed, or by nerves when your skin is very cold.)

12.10 THE HUMAN LIFE CYCLE

Aims:

• To revise the principles of sexual reproduction and internal fertilisation (from Module 5.5).

• To make students aware of the helplessness of human offspring as compared to the young of other mammals.

• To make students aware of the different stages in the life of a person.

Activities:

• Review the basic principles of sexual reproduction from Topic 5.

• Discuss with students their own experiences regarding the needs of infants and young children for adult protection and support. Review the summary provided in the text book regarding the stages in the life of a human being and get students to help you to elaborate on that with regard to their own communities.

12.11 THE MALE REPRODUCTIVE SYSTEM

Aims:

• To inform students about the male reproductive system including the location and functions of the main organs.

• To make students familiar with the main changes, including behavioural changes, that take place in boys during puberty.

Activities:

• Discuss with students the information provided in the textbook regarding the structure of the male reproductive system. The topics in the remainder of this chapter are viewed differently in different cultures. Teachers should use their own judgement to find the most appropriate compromise between, on the one hand simply reading through the topic in a neutral, ‘scientific’ way with minimal discussion, and at the opposite extreme, encouraging frank discussion of related social issues. In the same way, teacher’s should decide whether or not to show students the testes and penis of a sheep, goat or pig from the butchery.

• Discuss with students the information provided in the textbook regarding puberty as appropriate given the local context.

• Depending on local circumstances, it may be appropriate to invite a suitable medically qualified person to discuss related issues with your students after the current series of lessons.

• Encourage students to try the questions at the end of the module. Follow up by discussing their attempts and make sure they are aware of, and understand, the correct answers.

Answers:

• Q1. (i) The testes are the male sex organ in which the male gametes (or sperm cells) are produced. (ii) Erectile tissue is the tissue of which the penis is made; it contains a rich supply of blood vessels and when these are filled with blood the tissue expands and becomes hard. (iii) Semen is a milky fluid ejected through the penis during sexual intercourse; it contains sperm cells in a nutrient fluid produced by the seminal vesicle and the prostate gland.

• Q2. Acne is caused when oils secreted by the skin block pores which become infected by bacteria. Acne can be minimised by washing regularly. This is likely to be most effective if it is done before the infection becomes well established.

• Q3. The testes are suspended outside the body to keep cool. Sperm cells die if they become too hot.

• Q4. The changes associated with puberty are started by hormones from the pituitary gland (which stimulate the testes into growing and into producing male sex hormones called androgens).

12. THE FEMALE REPRODUCTIVE SYSTEM

Aims:

• To inform students about the female reproductive system including the location and functions of the main organs.

• To make students familiar with the main changes, including behavioural changes, that take place in girls during puberty.

• To make students familiar with the menstrual cycle including the three main stages (follicular stage, ovulation, luteal stage) and their timing.

Activities:

• Discuss with students the information provided in the textbook regarding the structure of the female reproductive system. The topics is viewed differently in different cultures. Teachers should use their own judgement to find the most appropriate compromise between, on the one hand simply reading through the topic in a neutral, ‘scientific’ way with minimal discussion, and at the opposite extreme, encouraging frank discussion of related social issues. In the same way, teacher’s should decide whether or not to show students the ovaries and uterus of a sheep, goat or pig from the butchery.

• Discuss with students the information provided in the textbook regarding puberty as appropriate given the local context.

• Discuss with students the information provided in the textbook regarding the menstrual cycle as appropriate given the local context. Students of both genders need to understand this topic.

• Depending on local circumstances, it may be appropriate to invite a suitable medically qualified person to discuss related issues with your students after the current series of lessons.

• Encourage students to try the questions at the end of the module. Follow up by discussing their attempts and make sure they are aware of, and understand, the correct answers.

Answers:

• Q1. (i) The ovary is the female sex organ in which the female gametes (ova/eggs) are produced. (ii) The follicle is a tiny sack in the ovary in which an ovum (egg) develops. (iii) The corpus luteum is a temporary endocrine gland that releases hormones to prepare a woman’s body for pregnancy. (iv) The oviduct is also called the fallopian tube. It is a tube leading from a woman’s ovary to her uterus. (v) The uterus is the organ in which a baby develops during pregnancy – it is also called the womb. (vi) The cervix is the muscular opening at the base of the uterus. (vii) The vagina is the passage in a woman’s body that leads from the vulva on the outside to the cervix on the inside. (viii) The vulva is the external part of a woman’s sexual organs – the part that becomes cover by pubic hair during puberty.

• Q2.

|Name of stage |Timing (approx) |Events occurring |

|Follicular stage |Days 1 - 12 |The wall of the uterus bleeds through the vagina (days 1 – 5) and then |

| | |thickens. An ovum develops inside a follicle. |

|Ovulation |Days 13 - 15 |A ripe ovum (egg) is released into a fallopian tube. |

|Luteal stage |Days 16 - 28 |If the ovum is fertilised, it may grow into a baby in the uterus. If not, the |

| | |menstrual cycle starts again. |

13. ONCEPTION, PREGNANCY AND BIRTH

Aims:

• To inform students about the main processes involved in conception, pregnancy and the birth of a baby.

Activities:

• Discuss with students the information provided in the textbook regarding conception, pregnancy and birth. These topics are viewed differently in different cultures. Teachers should use their own judgement to find the most appropriate compromise between, on the one hand simply reading through the topic in a neutral, ‘scientific’ way with minimal discussion, and at the opposite extreme, encouraging frank discussion of related social as well as physical issues.

• Depending on local circumstances, it may be appropriate to invite a suitable medically qualified person to discuss related issues with your students after the current series of lessons.

• Encourage students to try the questions at the end of the module. (The answers to question 2 in the last topic and question 2 in this topic, could provide a basis for discussing the so called ‘safe’ and ‘fertile’ times for sexual intercourse if this is appropriate in local circumstances! This will be followed up in question 2 in Topic 12.15) Follow up by discussing students’ attempts and make sure they are aware of, and understand, the correct answers

Answers:

• Q1. (i) A zygote is a fertilised ovum or egg cell. (ii) An embryo is a zygote after it has started to divide and become a multi-cellular organism. (iii) A foetus is an embryo that has started to develop all the organs it will have at birth – a human embryo becomes a foetus after the end of the 8th week. (iv) The amniotic fluid is the fluid the embryo or foetus floats in inside the womb. (v) You navel or tummy button is where your umbilical cord was attached when you were born.

• Q2. Sexual intercourse can lead to pregnancy only at a time when there is an ovum in the woman’s fallopian tubes at the same time as a man’s sperm. Since the ovum is usually released on days 13, 14 or 15 of the woman’s period, and since the sperm cells can live inside the woman’s body for about two days, the most likely time for pregnancy to occur will be between days 11 and 17 of the woman’s period (with day 14 as the most likely day).

• Q3. A woman may feel her baby moving for the first time about week 21. (In fact it is moving much earlier than this but this is not often noticeable by the pregnant woman).

• Q3. The role of the placenta is to link the blood system of the embryo or foetus to the blood system of the mother. The embryo/foetus depends on the mothers blood for food and oxygen, and for getting rid of its wastes. The role of the umbilical cord is to link the placenta to the embryo/foetus place on belly where umbilical chord was attached (through its tummy).

14. THE DEVELOPMENT OF INFANTS

Aims:

• To help students identify the basic needs of infants as nutrition (food), physical and emotional security, and stimulation, and to make them aware, in general terms, of how these needs are usually met.

• To inform students of some of the main milestones in the development of infants.

Activities:

• Discuss with students the information provided in the textbook regarding the development of infants. Emphasise their helplessness at birth and how they very gradually develop up to an age at which they are ready to go to school. Refer to examples from their own family experiences as far as possible.

• Discuss with students the information provided in the textbook regarding the needs of infants and how these are customarily met. (In the textbook, catering for an infant’s need for physical and emotional security has been taken for granted, but it would be desirable for the teacher to emphasise, in an appropriate way, the care and love that all infants need and are entitled to). Focus on and discuss relevant local circumstances and practices.

• Depending on local circumstances, it may be appropriate to invite a suitable medically qualified person to discuss related issues with your students after the current series of lessons.

• Encourage students to try the question at the end of the module. Follow up by discussing students’ attempts and make sure they are aware of, and understand, the correct answers.

Answers:

• Q1. (i) Weaning onto solid food usually takes place between 6 and 12 months. (ii) An infant usually starts to crawl between 6 and 12 months. (iii) An infant usually walks for the first time between 12 and 18 months. (iv) An infant usually starts to use simple sentences by about 2 years of age. (v) An infant usually starts to play cooperatively with other children between the ages of 3 and 4 years.

15. POPULATION ISSUES

Aims:

• To make students aware of the issue of world population and its trend in relation to the capacity of the Earth to sustain such numbers.

• To make students aware of the need for smaller families and of appropriate methods of birth control.

Activities:

• Discuss with students the information provided in the textbook regarding population and family size issues. The aim of this module is limited to promoting awareness of the issues involved on the basis of reliable information. However, students could be encouraged to research these issues in greater depth if that was considered appropriate.

• Depending on local circumstances, it might be appropriate to invite a suitable medically qualified person to discuss contraception and related issues with your students.

• Encourage students to try the questions at the end of the module. These questions could provide the basis for some interesting class discussions - in particular the issue of sustainable growth in question 1 and of contraception in question 2. Follow up by discussing students’ attempts and make sure they are aware of, and understand, the correct answers.

Answers:

• Q1. (i) Exponential growth is growth that gets faster and faster all the time …. until eventually something has to break down of course! Sustainable growth is growth that does not use up any raw material that will eventually run out. [The words sustainable and growth have somewhat contradictory meanings – all growth uses up raw materials and if the growth is continuous it can not last for ever, so the only growth that is truly sustainable is growth that has a limit]. (ii) Pollution is the spoiling of the world around us with our waste products. (iii) Family planning mean limiting the number of children we have by preventing pregnancy. Pregnancy can be prevented by using a reliable method of contraception.

• Q2. The fertile days of a woman’s period are days on which it is possible for as sperm cell to meet an ovum in the fallopian tubes. The ovum is usually released into the fallopian tubes on days 13, 14 or 15 of her period. But, sperm cells can live for about 2 days in a woman’s body, so if she has sexual intercourse on day 11 some sperm may still be alive in her fallopian tubes when the ovum is released there on day 13. Also, the ovum takes about 2 days to travel down the fallopian tubes so it might still be there to meet a sperm cell if she had sexual intercourse on day 17. Therefore days 11 to 17 are the most likely days for sexual intercourse to lead to pregnancy. The natural method is not completely reliable because most women’s periods vary slightly from month to month. Avoiding sexual intercourse on days 10 to 18 would be safer, and days 9 to 19 would be safer still! Restricting sexual intercourse to the last 10 days of a woman’s period is reasonably reliable (but no method is completely guaranteed!).

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SYSTEMS

ORGANS

TISSUES

CELLS

HUMAN BODY

composed of

composed of

composed of

composed of

CIRCULATORY

heart, blood,

blood vessels

RESPIRATORY

lungs, diaphragm

DIGESTIVE

mouth, stomach, intestines, liver

MALE REPRODUCTIVE

penis, testes

EXCRETORY

kidneys, bladder, lungs, liver, skin

LYMPHATIC

lymph, lymph vessels, lymph nodes

SKELETAL

bones, joints

MUSCULAR

muscles, tendons

ENDOCRINE

endocrine glands

examples, with main organs, are

FEMALE REPRODUCTIVE

vagina, ovaries, uterus

GENERAL FUNCTIONS

perform

supplemented by

SKIN

biggest one is

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