human reproduction -- chapter 5

sexual reproduction in human

process of producing genetically different offspring as a result of the fusion of gametes

fertilisation summarised

nucleus of sperm fuses with nucleus of an ovum to form a zygote that divides repeatedly by mitosis to form an embryo

sperm

• produced in testis

• head : nucleus + acrosome (contain digestive enzyme to breakdown outer jelly layer of ovum)

• middle : mitochondria to produce ATP

• tail/flagellum : drive the movement of sperm by swimming

• survive :2-3 days

Eggs

• ovary has many primary follicles

• each primary follicle consists of a potential egg cell

• egg cell covered by a fluid filled sac and enclosed in a jelly like coat

• mature ovum + fluid filled sac = Graafian follicle

• survive : 24-36hr

male reproductive cell parts

1. Testes

2. Scrotum

3. epididymis

4. vas deferens (sperm duct)

5. spermatid cod (supplies oxygen and nutrients to testes + remove waste)

6. seminal vesicle (gland 1)

7. prostate gland (gland 2)

8. cowpers gland (gland 3)—> below gland 2

testes description + function

• gonads in a male

• produces sperms and male sex hormones (testosterone)

scrotum

• pouch like extension of skin in between thighs

• protects testes

epididymis

• narrow and coiled tube from each of the testes

• stores sperms temporarily + force sperms out through urethra

vas deferens (sperm duct)

• duct from each testis loops over ureter and opens to urethra

• forces sperms out through urethra + facilitate passage of sperms from epididymis

epididymis first then vas deferens then urethra

seminal vesicle (gland 1)

• gland that opens into sperm duct / vas deferens

• secretes a slipper fluid that onrushes and activate sperms to swim

prostate gland

• at the base of the urinary bladder

• secretes a slipper fluid to nourish and activate the sperms to swim

cowpers gland

• beneath prostate gland

• secrete a slipper fluid to nourish and activate sperms to swim

female reproductive system function (3 parts)

• produce eggs

• provides an environment for fertilisation and the development of the embryo to take place

how does negative feedback system play a role in the female reproductive system

1. hypothalamus in the brain secretes hormones into the bloodstream

2. triggering the ovaries to produce female sex hormones into the bloodstream (oestrogen and progesterone)

female reproductive system parts

1. ovary

2. fallopian tubes

3. uterus

4. cervix

5. vagina

6. vulva

Ovary

• gonads , oval shaped , just below kidneys , 2 per female

• produce female gametes (before birth) and female sex hormones (oestrogen and progesterone)

fallopian tube

• narrow , ciliated muscular tube leading from ovary to uterus / funnel like opening close to the ovary

• facilitates passage of eggs into the oviduct , the site of fertilisation / allows passage of egg into the uterus

uterus

• joined to oviduct , muscular walls , soft and smooth endometrium, (inner lining that sheds every month)

• receives fertilised egg + provides a conducive environment for implantation of embryo and development of foetus

Cervix

• ring of muscles at lower end of uterus

• control size of opening

vagina

• passage leading from cervix to exterior

• receives semen during sexual intercourse

vulva

• opening of vagina

• allows passage of menses or baby to the exterior

signals release by the brain cause which gland to release hormones

pituitary gland , in turn act to stimulate primary sex organs (testes and ovaries)

when testosterone (hormone) is released what happens to target organs of boys/secondary sexual characteristics

1. rapid growth in height

2. hair in pubic area

3. penis and testis increase in size

4. testes produce sperm and hormones

5. facial hair grows

• target organs: muscles , penis , hair follicles

when oestrogen (hormone) is released what happens to target organs of females/secondary sexual characteristics

1. rapid growth in height

2. hair in pubic area

3. breast enlarge , hips broaden

4. uterus enlarges , menstruation starts

5. ovaries produce ovum and hormones

test/o/sterone is responsible for

1. development of male secondary sexual characteristics during puberty

2. ensure sperm production +maintain sex drive

3. formation of male genitalia during embryonic development (before birth)

Oestrogen is responsible for

development of female secondary sexual characteristics and repair of the endometrium

Prog/es/terone is responsible for

maintenance of the uterine lining in the preparation for pregnancy

menstruation defintion

monthly discharge of blood from the uterus via the vagina

• last for 5 days

• takes 3 years to stabilise

• stress/illness.tiredness impact amount of blood loss

• unbalanced diet cause periods to be irregular or stop

• menopause : menstruation pause (45-55 yr old)

menstrual cycle definition

process of releasing an egg and preparing the uterus for implantation of the fertilised egg

• last about 28 days and are divided int three phases (menstruation / follicular and luteal)

menstruation phase (1 to 5 days)

1. shedding of the uterine lining out of body through vagina

2. anterior pituitary gland secretes follicle stimulating hormones (regulate development and growth and puberty) into the bloodstream

follicular (day 6 to 14)

1. follicle stimulating hormone stimulates follicle development in the ovaries

2. one primary follicle matures into Graafian follicle (contains mature egg)

3. follicle stimulating hormone stimulates the follicles in the ovaries to secrete oestrogen, (day 6 to 10)

what does oestrogen do

1. growth and repair of uterine lining

2. rise in levels of oestrogen in the blood inhibits (stops ) follicle stimulating hormones production , preventing growth of more follicles (negative feedback loop)

3. high concentration of oestrogen stimulates the pituitary gland to secrete luteinising hormone , which stimulates ovulation

Day 14

Graafian follicle rupture and release the egg into fallopian tube . Body temperature increases , large amount of mucus produces and ovary pain experienced

Luteal phase (day 15 to 28)

1. after ovulation , the Graafian follicle develops into a corpus lutem

2. luteinising hormone stimulates the opus luteum to develop , then follicle secreting hormones and luthenising hormones drop if the egg is not fertilised

3. corpus lutem produces hormones that prepare the body for pregnancy (eg progesterone and oestrogen )

what does progesterone do

1. inhibits follicle stimulating hormones production and ovulation (in the event of successful fertilisation)

2. if no fertilisation occurs, the corpus lutes will persist for some time and then eventually break down , progesterone levels decrease and endometrium breaks down

copulation (sexual intercourse) and fertilisation

• sperm is released from the testes by peristalsis along sperm ducts and urethra

• seminal fluid is added to form 3-4ml of semen ejaculated from the tip of the erect penis

• fertilisation is the fusion f=of the ovum and sperm , occurring at fallopian tube

journey of egg

1. egg leaves ovary entering fallopian tube

2. sperm enters egg and unite with nucleus (fertilisation)

3. fertilised egg divides

4. cell attaches to the uterus /embeds itself in uterine lining (implantation)

conception

• some outer cells of the embryo combine with some of the mother cells for the development of the placenta

• embryo transferred to the thickened uterine lining for implantation via sweeping by cilia and peristalsis of smooth muscles in oviduct

• begins when implantation is completed

infertility treatment

• in-vitro fertilisation , ovum is fertilised in a special artificial dish

• the fertilised egg will be incubated for a few days , allowing it to divide and develop into an embryo before transplanting it back to the uterus for implantation

artificial insemination

carried out when there is a problem with the sperm and the donor sperm will be transferred into the women’s uterus during ovulation

contraception definition (birth control)

deliberate prevention of unintended pregnancy

methods of contraception

1. body’s natural cycles (rhythm method/menstrual cycle)

2. a physical barrier between sperm and ovum , to prevent implantation

3. use of chemicals (hormones)

4. surgical procedure (surgery to cut something)

Rhythm method

couples avoid intercourse during the fertile period (plus/minus 3 days from ovulation)

• calendar method : calculate time of ovulation

• temperature method : changes for ovulation (temp is higher on the day of ovulation)

• mucus method : change in mucus lining of vagina and cervix during ovulation

male contraceptive methods

1. withdrawal of the penis from vagina before ejaculation : unreliable , small amounts of semen can leak out

2. vasectomy : sperm duct is cut

3. condom : thin rubber fitted over erect penis , preventing sperm from being released into the vagina + STI

female contraceptive methods

1. diaphragm/cap (covers cervix , STI can still occur , physically prevent sperm from entering)

2. female condom

3. intrauterine device (inside uterus )

4. spermicide (chemical which kills sperm, applied on vagina)

5. contraceptive pill (hormone)

6. Morning after pill (prevent implantation)

7. capsule under skin

8. patch

gestation period

growth and development from conception takes 9 months

• growth : repeated division of the zygote

• development : organisation of cells into tissues and organs with special functions

signs of pregnancy

1. missed period

2. more frequent urination (uterine lining grows , more pressure on bladder)

3. tender breast

4. pregnancy test (measure amount of Human Chorionic Gonadotropin hormone in urine)

Placenta

found in mammals , serves to provide a stable internal environment for the foetus to grow

• supply nutrients , oxygen to the foetus , waster products diffuse into blood to be removed

placenta characteristics

disc like structure with finger like projections called villi

how is placenta formed

• Fetal cells from external surface of embryo

• maternal cells from uterine lining in early pregnancy

a fetus is surrounded by

amniotic sac filled with amniotic fluid , protection from injury/shock

umbilical cord

attaches fetus to placenta + cotains umbillical artery and vein

umbilical artery function

carries carbon dioxide and waste materials to the placenta fro excretion , away from fetus

umbilical vein function

carries oxygen , nutrients and antibodies to the fetus for metabolism and development

in the placenta , there is no direct contact between maternal blood and metal blood , why?

if they come into contact with each other the fetus will die/prevent immune response due to different antibodies in blood

blood flow in umbilical capillaries

opposite to the flow of maternal blood to maintain a concentration gradient for the exchange of substances

role of placenta

1. protection of fetus from attack by mothers immune system and against fluctuation of maternal pressure

2. secrete sex hormones to maintain thickness of uterine lining after 3rd month of pregnancy

abortion

termination of pregnancy when the mother is at high risk of developing severe health complications or even death when the fetus fails to develop normally or is at high risk of genetic defects

development stage of fetus + procedure

1. 9 weeks —> abortion pill

2. 9-14 weeks —> vacuum aspiration

3. 14-19 weeks —> dilation and evacuation

4. 20-24 weeks —> pills to induce late miscarriage

ante-natal care (before birth)

1. diet (proteins , iron and calcium)

2. avoidance of smoking

3. avoidance of infections

4. assistance of alcohol

5. avoidance of certain medical drugs

6. check on fetus + mother

avoidance of smoking

nicotine content may cause fatal growth to be slowed and produce small size Abbies who are retarded or abnormal or cause fatal death

avoidance of infections

may cause damage to fetal organs and produce deformed babies or the death of the fetus

• like STI / Rubella

avoidance of certain medical drugs

may cause retardation in babies , fatal addicted to the drug , miscarriages

• eg : antibiotics , aspirin

avoidance of drugs (cocaine + heroin)

cause congenital heart defects and urinary tract abnormalities , low birth weight , fatal distress

abstinence of alcohol

alcohol can easily pass across the placental barrier to the fetus , have impacts on nervous system

check on fetus

1. size / position —> fetus needs to be face head down , facing the mothers back

2. heartbeat measured by stethoscope (fetal heart rate twice as mothers )

3. ultrasound scanning : sex/size/age

check on mother

1. weight —>12kg gained throughout pregnancy

2. urine test : blood glucose

3. vaginal examination : infection

4. blood test : haemoglobin , blood groups

development of fetus in first month

• embryo-7mm

• nerve tube , heartbeat , limb buds present

development of fetus in second month

• fetus--13mm

• all organs present — tiny + immature

• bone begins to harder

• drugs may affect fetus

• muscles allow movement

development of fetus in third month

• fetus is about 70mm

• more movement

• lymph nodes formed

development of fetus in fourth month

• fetus is about 95mm

• vigorous movement felt by mother

• look more human

development of fetus in 7-9 months

pre term babies have a good chance of survival with medical assistance

labour

• initially, prevented by high levels of progesterone (maintains uterine lining) but its level decreases as birth approaches

• labour is induced by oxytocin (positive feedback) released from pituitary gland (stimulates contraction of uterus muscles)

increase in levels of oestrogen in labour

makes the uterus to be more sensitive to oxytocin by increasing the number of oxytocin receptors

what is expelled from utereus after child birth

1. placenta

2. amniotic sac

3. umbilical cord

STI

• caused by pathogens (virus+bacteria)

• can be acquired through semen/vaginal secretion/blood, especially when there is skin barrier that allows microbes to enter the bloodstream

• eg: AIDS, gonorrhoea

common methods of transmission of STI (sexually transmitted infection )

• unprotected sexual intercourse

• sharing of hypodermic needles

• blood transfusion with infected person

how to prevent STD (sexually transmitted diseases)

1. use condom

2. know sexual history of partner

3. public education

4. development of vaccine

5. offer HIV testing for individuals at risk

Gonnorhea

• STD caused by bacterium

• can be cured by antibiotics if detected early

AIDS (acquired immune deficiency syndrome)

• caused by HIV

• HIV damaged immune system of an infected individual over time by killing the immune cells

• common signs : persistent fever/brain infection/pneumonia

• prevention : keep to 1 sex partner, do not share needles , use condoms , dont share toothbrush