Human Reproduction

The Male Reproductive System This consists of: A pair of testes situated in a scrotum The epididymis, vas deferens, ejaculatory duct and urethra The accessory glands: seminal vesicles, prostate glands and Cowper’s glands Penis

The Male Reproductive System

The Testis Testis are the male sex organs, They occur in a bag like scrotum which lies outside the abdominal cavity The testes produce sperm, which cannot survive long at body temperature. Sperm leave the body in semen, a fluid produced by the seminal vesicles. Within each testis are found seminiferous tubules

The Testis These are lined by germinal epithelium cells These cells produce the spermatozoa by spermatogenesis Inside the seminiferous tubules, there are specialised cells called sertoli cells

nucleus containing DNA Sex cells – sperm In males, the sex cells are called sperm. tail middle piece head cell membrane nucleus containing DNA Sperm are produced in sex organs called testes.

The Testis These cells secrete the male sex hormone called testosterone When sexual maturity (puberty) occurs, testosterone is responsible for the development of male characteristics Such as The growth of hair on the face, armpits and pubic areas Lowering of voice Development of muscles which give males their shape such as broad shoulders

What happens during puberty? Humans are born with a complete set of sex organs. However, they do not usually become active until between the ages of 10 and 18. In males, the testes start to make sperm, and in females, the ovaries start to release eggs. This stage of development is called puberty. During this important time, many changes take place in the bodies of young men and women.

Ducts responsible for carrying the spermatozoa from the testis to the penis The tubes responsible for carrying the spermatozoa include: Epididymis Vas deferens ejaculatory ducts urethra

The Testis These cells are rich in glycogen This glycogen serves as nutrients for the spermatids as they develop into sperm cells Between the seminiferous tubules are intestitial cells called cells of Leydig

Tubes Responsible for carrying the spermatozoa The epididymis is a coiled tube lying outside the testis but within the scrotum It leads from seminiferous tubules, stores sperm temporarily Later passes the sperm into vas deferens

Tubes Responsible for carrying the spermatozoa- vas deferens The vas deferens (sperm duct) carries the spermatozoa from the epididymis through the abdomen into the ejaculatory duct

Tubes Responsible for carrying the spermatozoa- ejaculatory ducts The two ejaculatory ducts join the urethra just after it leaves the bladder Contraction of the muscular wall of the ducts forces its content (semen) through the urethra

Tubes Responsible for carrying the spermatozoa - urethra The urethra is a tube which runs through the penis and opens at the tip It is a common tube for the passage of urine or semen

Accessory Glands The tubes transporting the spermatozoa are joined by seminal vesicles: prostate glands and Cowper’s gland

Accessory Glands These glands: Secrete a fluid which promotes movement of the spermatozoa Secretes a fluid which provides nutrition to the spermatozoa

Functions of the accessory glands Seminal Vesicles Secretes a fluid that nourishes and enables sperm to move. Prostate gland Secretes an alkaline fluid that neutralizes the acidity. Cowper’s glands Two glands by prostate that secrete a fluid that neutralizes acidity.

The Penis The penis is the external reproductive organ of the male Made up of spongy tissue Becomes filled with blood causing the penis to become erect Then inserted into the female organ

The male reproductive system

The female reproductive system

An overview This system consists of: A pair of ovaries A fallopian tube or oviduct The uterus or womb The vagina or birth canal The vulva or external opening

The Ovaries The ovaries are the female sex organs Occur un the lower part of the abdominal cavity and are held in place by ligaments Each ovary is made up of a covering of germinal epithelium with a large number of follicles within it

The Ovaries The germinal epithelium produces the follicles Oogenesis takes place within the follicles to produce the ova Follicles secrete the female hormones oestrogen and progesterone

The Ovaries When puberty occurs, the female sex hormones are responsible for the development of female characteristics Such as: Increase in size of breasts Development of pubic and armpit hair And menstruation

The fallopian tubes (oviducts) The fallopian tubes convey ova from the ovaries to the uterus Upper part is expanded into ciliated funnels Partially enclosed ovaries

The Uterus Two fallopian tubes open into the uterus which is pear shaped, hollow organ with muscular walls The ling of the uterus is called endometrium, is richly supplied with blood vessels

The Uterus The neck of the uterus, called the cervix, extends into the vagina The uterus serves for the attachment of the embryo Fertilisation takes place

Gametogenesis

Gametogenesis Spermatogenesis refers to the process by which spermatozoa are produced from the germinal epithelium of the testis Oogenesis is the process where ova is produced from germinal epithelium of the ovaries

Spermatogenesis At puberty, the germinal epithelial cells lining the seminiferous tubules start to produce spermatozoa by meiosis Each germinal epithelium is diploid and in humans the diploid number is 46 Since the sperm is produced by meiosis, each one will be haploid with 22 single chromosome and X or Y chromosome

Spermatogenesis The process is as follows: Cells of germinal epithelium become actively dividing cells called spermatogonia Each spermatogonium, which is diploid (2n), enlarges to become a primary spermatocyte (also 2n)

Spermatogenesis Primary spermatocyte undergoes the first meiotic division forming 2 haploid secondary spermatocytes Each secondary spermatocyte undergoes the second meiotic division to produce 2 spermatids Each spermatid matures to form a spermatozoan Each spermatozoan is made up of a head, a middle-piece and a tail

Hormonal Control of the Menstrual Cycle Inside the ovary of females there are large sac like structures called Graafian follicles Each follicle contains a maturing ovum The growth of he ovum inside the Graafian follicle is controlled by follicle stimulating hormone (FSH) Secreted by anterior lobe of the hypophysis or pituitary gland These are produced by the germinal epithelium

Hormonal Control of the Menstrual Cycle Between day 11 and 16, ovulation takes place During ovulation, a single graaffian follicle ruptures and sets free an ovum The ovum is collected by the funnel of the fallopian tube and passes down toward the uterus

Hormonal Control of the Menstrual Cycle Luteinising hormone (LH), also produced by the anterior lobe, helps convert ruptured follicle into a structure called corpus luteum

Hormonal Control of the Menstrual Cycle If the ovum is fertilized by a sperm cell Corpus luteum secretes hormone progesterone Makes certain that the embryo remains attached to the uterus wall Ensures pregnancy remains

Hormonal Control of the Menstrual Cycle If the ovum is not fertilized, the corpus luteum is destroyed Little progesterone is secreted and menstruation occurs During menstruation, the endometrium lining of the uterus comes off as the menstrual period

Hormonal Control of the Menstrual Cycle This is accompanied by bleeding Menstruation takes place about 14 days after ovulation The next egg is then released about 14 days after menstruation

Hormonal Control of the Menstrual Cycle There are 2 separate sub-cycles during the menstrual cycle The ovarian cycle The uterine cycle

Hormonal Control of the Menstrual Cycle The ovarian cycle describes what happens in the ovary The uterine cycle describes the changes that are made in the uterus lining A graafian follicle, at different stages, produces oestregen and progesterone

Hormonal Control of the Menstrual Cycle These hormones control what happens ti the uterine wall The cycles are closely related The entire menstrual cycle is controlled by hormones produced by anterior lobe of hypophysis

Fertilisation and implantation

Fertilisation and implantation During sexual intercourse/ copulation. Penis is placed into vagina and spermatozoan is released It swims up to uterus and into fallopian tube

Fertilisation and implantation If an ovum is present in this time, the sperm will fertilise it Resulting in a diploid zygote The moment of fertilisation is called conception Spermatozoan has 22 single autosomes and X or Y chromosome Ovum has 22 single autosomes and an X chromosome

Fertilisation and implantation Fertilisation usually takes place in the upper part of the fallopian tube There is not enough space here for a baby to grow It has to move down to the uterus for more

Fig. 29.19

Fertilisation and implantation It is moved down the fallopian tube by beating oh fine hair-like structures on the walls As it passes down into the uterus, it divides by mitosis This happens many times

Fertilisation and implantation All cells are identical By the time it reaches the uterus it is a hollow ball of cells called blastocyst By the ninth day, th blastocyct is now called and embryo

Fertilisation and implantation The process of developing the embryo and becoming attached to the uterine wall is called implantation In the meantime, the corpus luteum has secreted progesterone

Fertilisation and implantation The endometrium lining of the uterus has become thicker and supplied with blood vessels

Embryonic development and Pregnancy

Embryonic development and Pregnancy Another term for pregnancy is the gestation period It lasts for about 280 days which is slightly more than 9 months

Embryonic development and Pregnancy Embryo increases in shape and size as it grows By 12 weeks the embryo has grown quite a lot, and will look clearly like a human baby It is now called the foetus

Development of the extra-embryonic membranes

Development of the extra-embryonic membranes Soon after the blastocyst itself to the uterus wall, 2 membranes develop around it Extra-embryonic membranes

Development of the extra-embryonic membranes These membranes are: The chronian on the outside, forms chronic villi An amnion, on the inside, with amniotic cavity filled with amniotic fluid

Development of the extra-embryonic membranes Chronic villi with uterine tissue make up the placenta A hollow rope-like tube called umbilical cord, attaches the embryo to the placenta

Development of the extra-embryonic membranes The placenta has the following functions: Attachment of embryo to mother Diffusion of desolved food from mother to foetus

Development of the extra-embryonic membranes Diffusion of oxygen from mother to foetus and carbon dioxide from foetus to mother

Development of the extra-embryonic membranes After 12 weeks of pregnancy it secretes its own progesterone which maintains pregnany

Development of the extra-embryonic membranes The amniotic fluid has the following functions: Shock absorber Prevents dehydration

Development of the extra-embryonic membranes Keeps foetus within a small temperature range Allows free foetal movement for growth and development

Development of the extra-embryonic membranes The umbilical cord contains the umbilical artery and vein The artery carries deoxygenated blood with nitrogenous wastes from the embryo to the placenta The vein carries oxygenated blood and food

Birth Occurs about 280 days after fertilisation, this happens in 3 stages Stage 1: Uterus contracts Head pushed against cervix Membranes break Cervix dilates

Birth Stage 2: Baby forced out through birth canal Umbilical cord cut Baby handed to mother Stage3: Placenta becomes loose Placenta pushed out as the ”after-birth

Contraception Natural Methods Withdrawal Description Natural Methods Withdrawal The penis is removed out of the vagina before ejaculation but it is not safe method because many sperms are released during sexual intercourse Rhythm method Sexual intercourse is avoided during ovulation. This is not a safe method of contraception because it is impossible to be 100 % sure when ovulation will occur

Contraception Barrier methods Condom Description Barrier methods Condom Act as a barrier to stop sperms from entering the vagina Femidom Act as a barrier to stop sperms from getting into the uterus/Fallopian tubes IUD/loop It prevents fertilised eggs/embryos from becoming attached to the uterine wall and is highly effective Diaphragm It covers the cervical opening and prevents sperm from entering the uterus and is fairly effective

Contraception Method Description Chemical/drug treatment Spermicides It contains a chemical substance that kills sperm and acts as a barrier/prevents sperm from entering the Fallopian tubes. They are not very reliable on their own. Contraceptive pills Contains artificially produced hormones which prevents the production of eggs/ovulation. Signalling the body that it is already pregnant. It changes the lining of the cervix/womb. It is a very reliable method. Contraceptive injections It contains progesterone/combination of oestrogen and progesterone which stops ovulation/changes the lining of the womv and the cervix. It works for 2 to 3 months and are very effective.

Contraception Surgical methods Male Sterilisation Description Surgical methods Male Sterilisation The sperm ducts are cut and tied. Semen without sperm is produced and is a very effective method of contraception. Female Sterilisation The Fallopian tubes are cut and tied during a small surgical operation preventing the fusion of sperm and egg

syphilis Caused by spiral bacterium, treponema pallidum Transmission: Sex with infected partner, mother to child Symptoms: Nodules on sex organs Rash over the body Sore throat and aching muscles

syphilis Can attack tissue or organ including skin Lead to blindness and death Treatment: Antibiotics in early stages

gonorrhoea Causes: Coccus bacterium, gonococus Transmission: Sex with infected person Symptoms: Frequent and painful urination, discharge Sterility in men and woman

gonorrhoea Treatment: Antibiotics, penicillin More difficult to cure in late stages

Prevention of stds Most stds are life-threatening For many of them, there is no cure Medication, nutritious diet and healthy lifestyle can slow down progress of the disease Use A B C method Abstain from sexual activites Be faithful to your partner Condomise