Sexual Reproduction in the Human Pregnancy, Birth & Breastfeeding

Learning Objectives Explain copulation State the location of fertilisation Explain implantation, placenta formation & function Outline the birth process Explain In-vitro fertilisation & implantation Outline milk production & breastfeeding including biological benefits

Copulation – Sexual intercourse Sexual arousal – The penis becomes erect – The vagina becomes lubricated Copulation – The penis is inserted into and moved inside the vagina Orgasm – Sperm is released from the penis (Ejaculation) – Contraction of vagina and uterus

Insemination Insemination is the release of sperm into the female Contractions of uterus and fallopian tubes move the sperm to the fallopian tubes within 5 minutes If an egg is present it releases chemicals to attract the sperm this is called chemotaxis

Fertilisation Fertilisation is the fusion of the egg and sperm nuclei to form a diploid zygote.

Fertilisation Fertilisation usually occurs in the fallopian tube. Fertilisation is complete when the ovule has been fertilised

Fertilisation A number of sperm may reach the egg at the same time. The acrosome releases enzymes to digest the egg membrane The sperm loses its tail and the head enters the egg. The sperm and egg nuclei fuse to form a zygote A chemical reaction at the membrane prevents other sperm cells entering.

Implantation Implantation is the embedding of the fertilised egg into the lining of the uterus This occurs days after fertilisation. By this time the zygote has grown into an embryo. After implantation the placenta forms. During implantation a membrane called the amnion develops around the embryo. This secretes amniotic fluid which will surround the developing embryo and act as a shock absorber.

Implantation is the embedding of the fertilised egg into the lining of the uterus Zygote Implanted embryo

Human Pregnancy Zygote divides by mitosis to form a morula. The morula moves down the fallopian tube and implants in the uterus Morula: Solid ball of cells It develops into a blastocyst Blastocyst: Fluid-filled ball of cells

Human Pregnancy (HL) Blastocyst consists of – Trophoblast (will develop into placenta) – Embryo cells (will develop into embryo) Blastocyst imbeds itself into uterus lining (endometrium)

Placenta Formation After implantation the embryo forms an outer membrane called a chorion This chorion develops projections (chorionic villi) which, together with the blood vessels of the mother in the endometrium, form the placenta

Placenta Functions: – It is an organ that allows exchange of materials between the foetus and mother – It produces hormones such progesterone – Allows passage of food and oxygen – Allows passage of antibodies – Removes waste produced by embryo

Placenta It is formed from tissues of the mother and the embryo (uterine tissue and embryonic tissue)

Placenta Formation The blood of the mother and embryo do not mix This is important as: – The blood groups of mother and baby might not be compatible. – The blood pressure of the mothers system may cause damage to the embryo

Placenta Formation The umbilical cord connects the placenta with the embryo. It contains blood vessels which circulate blood between the embryo and the placenta

Amnion It is a sac or membrane It produces fluid and protects embryo by acting as a shock absorber

Placenta Mother’s blood Embryo’s blood Chorion Embryo Amnion Amniotic fluid Umbilical cord Embryo Mother Nutrients, Oxygen, antibodies Wastes, Carbon Dioxide, Water The Placenta

Learning Check

Development of Embryo (HL) Blastocysts organise themselves into germ layer. Germ Layers are a layer of cells in the embryo with the potential to give rise to specific tissues 3 types of layers: 1.ectoderm – skin and nervous system 2.mesoderm – muscles skeleton 3. endoderm – inner lining of liver and lungs

Development of Embryo (HL) 3 weeks: Developed nervous system, alimentary canal, circulation. Heart beats. 8 weeks: Embryo is recognisable. Now called foetus 12 weeks: Swallows, inhales. Arms, legs move. Sex organs identified. 3-9 months: Continue to grow and develop

Birth 1The hormones oestrogen and progesterone are produced throughout pregnancy firstly by the corpus luteum (3 months) and then by the placenta. The placenta acts as an endocrine gland. 2Immediately before birth the placenta stops making progesterone. The walls of the uterus begin to contract as a result. 3The pituitary gland releases the hormone called oxytocin. This causes further contractions of the uterus. (HL) Labour has now begun.

There are three main stages: Stage 1 - (about 12 hours) The contraction of the uterus pushes the foetus towards the cervix. This causes the cervix to open (dilate). During this stage the contractions cause the amnion to break releasing the amniotic fluid through the vagina. (The ‘water’s break’).

Stage 2 - (20 minutes to 1 hour) The foetus passes through the cervix and the birth canal head first.

Stage 2 - (20 minutes to 1 hour) The foetus passes through the cervix and the birth canal head first.

Stage 2 - (20 minutes to 1 hour) The foetus passes through the cervix and the birth canal head first.

Stage 2 - (20 minutes to 1 hour) The foetus passes through the cervix and the birth canal head first.

Stage 2 - (20 minutes to 1 hour) The foetus passes through the cervix and the birth canal head first.

Stage 2 - (20 minutes to 1 hour) The foetus passes through the cervix and the birth canal head first. The umbilical cord is tied and cut. This leaves a scar which will eventually become the navel (belly button).

Stage 3 - (10 to 15 minutes) The baby is now born. The uterus now contracts again and expels the afterbirth (the umbilical cord and placenta).

Stage 3 - (10 to 15 minutes) The baby is now born. The uterus now contracts again and expels the afterbirth (the umbilical cord and placenta).

Stage 3 - (10 to 15 minutes) The baby is now born. The uterus now contracts again and expels the afterbirth (the umbilical cord and placenta).

Stage 3 - (10 to 15 minutes) The baby is now born. The uterus now contracts again and expels the afterbirth (the umbilical cord and placenta).

Umbilical cord is cut

Breastfeeding Lactation: secretion of milk by the mammary glands The secretion of milk from the mammary glands The first days after birth colostrum produced Milk production triggered by release of prolactin by pituitary (HL)

Breastfeeding Breastfeeding is better than bottle feeding because: Colostrum and breast milk provides the baby with essential antibodies protecting it against infection Ideal balance of nutrients for baby Bonding between mother and baby Reduces chances of breast cancer in the mother

Learning Check 1.What is fertilisation and where does it occur 2.When is fertilisation complete 3.What is implantation 4.4. What is a Morula &Blastocyst 5.5. List 3 functions of the placenta 6.6. What tissues is the placenta formed from 7.7.What is amnion and its function 8.List and explain the 3 stages of birth 9.List 3 benefits of breastfeeding

Can you…. Explain copulation State the location of fertilisation Explain implantation, placenta formation & function Outline the birth process Explain In-vitro fertilisation & implantation Outline milk production & breastfeeding including biological benefits