Chpt. 42: Human Reproduction

Organisation Both the male and female reproductive system are composed of: a pair of structures to produce sex cells. a series of transport tubes glands which secrete hormones

Male Reproductive System LS

The Male Reproductive System Main Parts: Testes Scrotum Epididymis Sperm Duct (vas deferens) Associated Glands Sperm Penis

The Male Reproductive System Testes (Testis): consists of a coiled mass of tubules produces sperm by meiosis makes testosterone (hormone) Scrotum: contains the testes temperature in scrotum is 35o C i.e. below body temperature. Epididymis: located outside each testis stores and matures sperm cells

The Male Reproductive System Sperm Duct (vas deferens): transports sperm from the testes to the urethra Note: urethra is tube located in centre of penis and is responsible for carrying urine or sperm out of body) Associated Glands: Seminal Vesicles – provides liquid for sperm to swim in and produces fructose which gives sperm energy Prostate Gland – produces liquid to nourish sperm Cowper’s Gland – produces a fluid to lubricate the urethra Note: when seminal fluid is added to sperm cells the resulting liquid is called semen.

The Male Reproductive System Sperm (Spermatozoa): Sperm are produced by meiosis in the testes sperm are haploid cells i.e. they only contain 23 chromosomes.

The Male Reproductive System Penis: carries sperm into the female reproductive system. swollen tip of penis called glans. foreskin (fold of skin) partially covers the glans.

The Male Reproductive System Male Hormones: At puberty: two hormones are produced by the male pituitary gland: FSH(Follicle Stimulating Hormone): stimulates the sperm-producing cells in the testes to divide by meiosis and produce sperm. LH (Luteinising Hormone): stimulates the production of testosterone in the testes. Before puberty: the testes produce small amounts of the hormone testosterone. Testosterone: causes primary and secondary male characteristics.

Sexual Characteristics Primary sexual characteristics: are the growth of reproductive organs. Secondary sexual characteristics: are the features that distinguish males from females apart from the sex organs themselves. Secondary male characteristics: growth of pubic, facial and body hair enlargement of larynx growth spurt widening of the shoulders increased sebum production – acne increased muscular and bone development

Infertility is the inability to produce offspring Male infertility: - Low Sperm Count Cause: - persistent smoking of cigarettes - alcohol abuse - use of marijuana or anabolic steroids - low levels of male hormones - mumps in adult life Treatment: changes in diet and lifestyle i.e. no smoking, no drugs, reducing alcohol intake, reducing stress levels. Hormonal therapy In-vitro fertilisation

Female Reproductive System LS

The Female Reproductive System Main Parts: Ovaries Fallopian Tubes Uterus (womb) Cervix Vagina

The Female Reproductive System Ovaries: produces eggs (ovum) by meiosis produces female hormones after puberty (11-12 yrs.) approx. 20 eggs produced by meiosis each month – only 1 survives. This haploid egg is surrounded by a Graafian follicle which produces the female hormone oestrogen. This Graafian follicle matures on the surface of the ovary and bursts at ovulation to release the egg. After ovulation this follicle becomes the corpus luteum – secretes the hormone progesterone.

The Female Reproductive System Fallopian Tubes: moves egg down tube by cilia and muscular peristalsis. site of fertilisation funnel of Fallopian tube catches the egg after ovulation. Oviduct : Fallopian tubes and uterus.

The Female Reproductive System Uterus (Womb): lined with the endometrium which nourishes the embryo. Cervix: opening into the uterus. Vagina: muscular tube which allows entry of sperm into the female system birth canal

The Female Reproductive System Vagina: Labia – folds of skin which protect vagina and are collectively known as the vulva. Hymen – ring of tissue which may partially block the vagina entrance.

The Female Reproductive System The Menstrual Cycle The menstrual cycle is a series of changes that happen about every 28 days in the female body. The menstrual cycle takes place: between puberty and the menopause only when a female is not pregnant

The Female Reproductive System Main events in the average menstrual cycle: Days 1 to 5: If fertilisation does not occur blood and tissue from the inner lining of the uterus (endometrium) is released – Menstruation (period). Meiosis in ovary produces new egg which becomes surrounded by Graafian follicle. Days 6 to 14: Graafian follicle produces oestrogen, causing the endometrium to thicken.

The Female Reproductive System Main Events in the Menstrual Cycle Day 14: Ovulation occurs – this is the release of an egg from the ovary Egg passes into the funnel of the fallopian tube. Endometrium continues to thicken. Day 14 – 28: Graafian follicle develops into corpus luteum and produces progesterone. Progesterone causes endometrium to thicken even more and prevents new eggs forming.

The Female Reproductive System Main events in the Menstrual Cycle If fertilisation has not occurred: around day 22 corpus luteum begins to break down. Progesterone levels decrease, causing endometrium to break down. Menstruation and cycle begins again.

The Female Reproductive System Female Hormones: Oestrogen: - causes endometrium to thicken in first half of cycle. - at puberty high oestrogen levels cause the primary female sexual characteristics. - prevents eggs from developing. Progesterone: - causes the endometrium to thicken for the last 14 days. Combination of oestrogen and progesterone at puberty: - causes secondary female characteristics.

Sexual Characteristics Secondary Female Characteristics: Growth of pubic and underarm hair widening of hips maturing and enlargement of breasts increased body fat growth spurt

Infertility Female Infertility: - The failure to release eggs i.e. ovulate Cause: - hormonal disorder (endocrine gland failure) i.e. failure to produce FSH – no eggs failure to produce LH – no ovulation - stress - tumour on ovary - no obvious cause Treatment: - for hormonal disorder- hormonal treatment. - reduce stress - surgery on the ovary - in-vitro fertilisation

Hormonal Control of Menstrual Cycle (Higher Level Only) Four hormones are involved in the menstrual cycle: - 1. FSH – follicle stimulating hormone - 2. Oestrogen - 3. LH – luteinising hormone - 4. Progesterone

FSH: - produced by the pituitary gland - produced early in cycle – days 1 – 5 Oestrogen: - produced by the graafian follicle - produced from days 5 – 14 - causes the endometrium to develop and inhibits FSH production - increased levels of oestrogen at day 14 cause LH to be produced FSH causes eggs to develop which are surrounded by graafian follicles Graafian follicles secrete oestrogen (indirectly FSH controls oestrogen production)

3. LH: - produced by the pituitary gland. - produced on day 14 - it causes ovulation to occur and the remains of the graafian follicle to become the corpus luteum 4. Progesterone: - produced by the corpus luteum - produced from days 14 to 28 - maintains the structure of the endometrium - inhibits the production of FSH and LH - prevents contractions of the uterus

If pregnancy does not occur the corpus luteum breaks down – day 22 Day 28 – as a result of low levels of progesterone and oestrogen the following happens: - FSH secretion is no longer inhibited - new eggs begin to develop - uterus contracts and endometrium is shed from the body - menstruation

Menstrual Disorder – Fibroids Fibroids are benign tumours of the uterus. Cause: unknown although may be associated with oestrogen levels Treatment: - small fibroids frequent check ups - large fibroids – surgery - large no. of fibroids – possible hysterectomy Symptoms: none when small but when large cause prolonged periods, pain, heavy periods, miscarriage, infertility

Sexual Intercourse (Copulation) Common Level Copulation (sexual intercourse): is where the erect penis of the male is placed in the vagina of the female. Stages of Copulation: Sexual Arousal: - in the male blood flow into penis increases and out of penis decreases – penis becomes erect - in the female vagina becomes enlarged and produces lubricants Copulation (Coitus or sexual intercourse): - penis moves inside the vagina - breathing and heart rates increase

Sexual Intercourse 3. Orgasm: - is the climax of sexual excitement. - in the female the outer vagina and uterus contract - ejaculation occurs – this is the emitting of semen from the penis. 4. Behaviour of sex cells: - insemination occurs – this is when semen is released into the vagina just outside the cervix. - sperm is pushed to an egg (if present) in fallopian tube. - if egg present it releases a chemical attracting the sperm – chemotaxis.

Fertilisation Fertilisation: occurs when the nucleus of the sperm fuses with the nucleus of the egg, forming a diploid zygote. normally takes place in the fallopian tube. many sperm swarm egg but only one enters egg upon entering sperm loses its tail and the membrane of the egg undergoes a rapid chemical change forming a fertilisation membrane This membrane prevents other sperm from entering.

Fertilisation Fertile Period Sperm can survive in female reproductive system for up to 3 days therefore pregnancy can occur if female has intercourse 3 days before ovulation. Egg can survive for 2 days therefore pregnancy can occur if female has intercourse 2 days after ovulation. As a result, in a typical menstrual cycle fertile period lasts from day 11 to day 16. Due to irregular menstrual cycles the fertile time is really days 9 to 18

Birth Control Birth Control: involves taking steps to reduce the number of children born. Abortion: involves the termination of a pregnancy. Contraception: is the deliberate prevention of fertilisation or pregnancy. There are four methods: Natural Mechanical Chemical Surgical Abortion Contraception

Birth Control Natural Contraception: involves not having intercourse around the time of ovulation. natural methods of contraception try to identify the time of ovulation based on: - body temperature - mucous secreted in the cervix - past menstrual cycles (rhythm method) Mechanical Contraception: involves using physical barriers to prevent sperm reaching egg. condoms diaphragms caps

Birth Control Chemical Contraception: involves the use of spermicides or hormones. Vaginal spermicides The pill Surgical Contraception: involves sterilisation of the female and vasectomy for males. Tubal Ligation Vasectomy

Implantation Implantation: is the embedding of the fertilised egg into the lining of the uterus. occurs 6 to 9 days after fertilisation during implantation amnion develops around the embryo amnion secretes amniotic fluid which protects the embryo.

Early Development of the Zygote Higher Level Only Fertilised egg contains 46 chromosomes Zygote divides many times by mitosis to form a ball of cells called the morula (after 3 days) Approx 5 days after fertilisation and further mitosis, morula forms a hollow ball called blastocyst Implantation occurs – blastocyst embeds in uterus Inner cells form the embryo and outer cells form amnion which secretes amniotic fluid which protects embryo Placenta forms from embryonic and uterine tissues

Placenta produces hormones (oestrogen and progesterone) and allows the exchange of materials between mother and baby to occur – wastes, antibodies, nutrients etc.

Embryonic Development Higher Level Only 10 days after fertilisation cells of inner cell mass of the blastocyst form embryonic disc which gives rise to three layers of cells called primary germ layers. Each of these layers give rise to different tissues: GERM LAYER TISSUE/ORGAN Ectoderm Skin, nails, hair & nervous system Mesoderm Muscles, skeleton, excretory , respiratory & circulatory systems Endoderm Liver, pancreas, inner lining of digestive, respiratory & excretory tracts

4th week – heart is formed and beating - umbilical cord formed 5th week – internal organs and limbs have started to form 6th week – eyes visible - mouth, nose, ears are forming 8th week – all major organs are formed and is now called a foetus 12th week – eyes low and widely spaced, cartilage replaced by bone (ossification), nerve and muscle coordinate, movement of the legs & arms, sex organs distinguishable, baby teeth begin to grow, the foetus sucks its thumb and can kick, breathe and urinate

After week 12 the baby continues to grow Pregnancy – Gestation: is the length of time spent in the uterus from fertilisation to birth ( 9 months – 40 weeks)

Birth Common Level For the first 10 - 12 weeks oestrogen and progesterone are produced by the corpus luteum, after that they are made by the placenta Before birth the production of progesterone stops and oestrogen increases – walls of uterus begin to contract Pituitary gland of mother produces hormone called oxytocin – causes contractions of uterine muscle resulting in onset of labour.

Birth Labour may be divided into three stages: Stage 1 - foetus rotates towards cervix - cervix widens - amniotic fluid is released - contractions begin Stage 2 - contractions become stronger & more frequent - foetus is pushed head first through the vagina Stage 3 - the placenta & foetal membranes are expelled (after birth)

Lactation is the production of milk by the mothers breast (mammary glands) prolactin produced by the pituitary gland stimulates milk production for first few days after birth colostrum produced from breasts. This has less fat and sugar than breast milk but is higher in minerals, proteins and antibodies.

Benefits of Breastfeeding provides baby with antibodies to protect against infection promotes a close bond between mother & baby it can reduce the risk of breast cancer in the mother uterus recovers faster as oxytocin stimulates uterine muscle contractions as well as stimulating milk secretion during lactation

In-Vitro Fertilisation (IVF) See notes for IVF Method is a method of treating infertility. it involves removing eggs from an ovary and fertilising them outside the body. IVF may be used: in females if fallopian tubes are blocked or the ovaries cannot produce eggs naturally in males if they have low sperm counts See notes for IVF Method

Note: umbilical cord connects the embryo with the placenta Placenta Formation After implantation embryo forms an outer membrane called the chorion completely surrounding amnion and embryo. Chorion develops projections called villi Together these villi and the mother’s blood vessels form the placenta Placenta does not become fully functional until about 12 weeks Note: umbilical cord connects the embryo with the placenta

Placenta Functions of the Placenta: allows materials to pass from the mothers blood to the embryo e.g. oxygen, food, antibodies drugs etc. and from the embryo’s blood to the mothers e.g. CO2, salts, urea. produces hormones prevents the blood supplies of the embryo and mother from mixing. This separation is essential because: - they might have different blood groups and bloods would clump if mixed - blood pressure of mothers system would cause damage to embryo.