4.1 SEXUAL HUMANS

Scrotum and function

External sac of skin hold testes out body

• Keep testes 2°C cooler than body temp

• Essential for spermatogenesis (make sperm)

Testes

Male reproductive organs produce sperm and hormones

• Produce sperm in seminiferous tubules

• Produce testosterone

Testes histology

• Seminiferous tubules → site of sperm production

• Sertoli cells → support developing sperm

• Leydig → Secrete testosterone

Epididymis

Long coiled tube back each testis

• Store sperm

• Sperm mature gain motility

Vas deferens

Muscular tube transport sperm

• Carries sperm from epididymis → urethra during ejaculation

Seminal vesicle

Gland produce seminal fluid

• Secret fluid reach fructose( sperm energy)

• Make most semen volume

Prostate gland

Gland below bladder

• Produce alkaline fluid neutralise acidic conditions in vagina → protect sperm

Urethra

Tube run through penis

• Carries semen and urine (not same time)

Penis

External male organ for reproduction

• Deliver semen into vagina

• Erectile tissue fill with blood → erection

Testis histological examination step

Seminiferous tubules circular

Central lumen

Cells in layers (stages of spermatogenesis)

Sperm near lumen

Leydig between tubules

Sertoli cells large support

• Germinal epithelium cells outer (primary spermatocytes)

• Spermatozoa tails seen lumen

Circ

Male reproductive system

Seminal vesicle

Prostate gland

Ejaculatory duct

Vas deferens

Epididymis

Seminiferous tubules

Testis

Urethra

Adaptions of testes

Lots of seminiferous → Large surface area

Cells different development stages

Sertoli cells support sperm

Leydig produce testosterone

Lumen allow sperm release

Ovary

Female reproductive organ produce eggs and hormones

• Produce eggs for fertilisation

• Secrete oestrogen and progesterone control menstrual cycle

Oviducts

Tube connect ovaries to uterus

• Site of fertilisation

• Move egg to uterus via cilia and muscular contractions

Uterus

Muscular organ where foetus develop

• Site of implantation (not fertilisation)

• Provide nutrients and protection for developing embryo

Endometrium

Inner lining of uterus

• Thickens each cycle to prepare implantation

• Shed during menstruation (if no implantation)

Cervix

Narrow neck connect uterus and vagina

• Produce mucus (change during cycle)

• Keep foetus in uterus during pregnancy

Vagina

Muscular tube connect uterus to outside body

• Receive penis during intercourse

• Act as birth canal

• Exit for mendtrual flow

Pathway of egg and hormone link

Ovary → Oviduct → Uterus → Cervix → Vagina

• Oestrogen → rebuilds endometrium

• Progesterone → Maintain endometrium

Histology of Ovary

Outer germinal epithelium

Primary follicles

Secondary follicle

Histology of Secondary follicle

Outer theca cells support follicle

Antrum - fluid filled cavity help. oocyte detach

Secondary oocyte

• Haploid metaphase 2

• Surround zona pellucida (glycoprotein layer) corona radiata

Three layers of uterus walls

• Perimetrium thin outside

• Myometrium muscle layer

• Endometrium innermost good blood supply shed

Spermatogenesis definition

Process spermatozoa are produced from diploid germinal epithelium in seminiferous tubules of testes

Stages of seprmatogenesis

Spermatogonia (2n) Stem

• Divide by mitosis

Primary spermatocytes (2n)

• Meiosis I

Secondary spermatocytes (n)

• Undergo meiosis II

Spermatids (n)

• no tail

• Maturation

Spermatozoa (n)

• Full developed motile

How many sperm cells does one spermatogonium produce

4 spem cells

Sertoli cells

In seminiferous tubules

• Nourish developing sperm

• Support spermatogenesis

• Blood testis barrier

Leydig cells

Between tubules

• Secrete testosterone

Testosterone funciton

Stimulate spermatogenesis

Control male secondary sexual characteristics

Structure of mature sperm cell

Head

• Haploid nucleus → genetic material

• Acrosome→ enzyme to penetrate egg

Midpiece

• Mitochondria packed → ATP for movement

Tail - flagellum

• Enable movement

Oogenesis

Process secondary oocyte produced in ovary

Stages of oogenesis

1. Germinal epithelium

• Outer layer of ovary produce oogonia

2. Oogonia(2n)

• Diploid stem

• Mitosis( before birth)

3. Primary oocyte (2n)

• Start meiosis 1

• Arrested in prophase until puberty

4. After puberty - Primary oocyte completes meiosis 1

• Secondary oocyte (n)

• First polar body (n)

5. Secondary oocyte

• Start meiosis 2 stop at metaphase 2

Next stage to secondary oocyte if fertilisation occur

Meiosis 2 completed

Second polar body formed

Ovum (n)

Follicle development

Primary follicle

• Primary oocyte surround by follicle cells

Secondary follicle

• More granulosa cell layers

• Beginning of fluid space

Graafian mature

• Large antrum (fluid filled cavity)

• Secondar oocyte ready for ovulation

Corpus luteum

• Form follicle after ovulation

• Secrete progesterone (maintain endometrium)

Structure of secondary oocyte

Corona radiata

• Follicle granulosa cells layer protect and nourish ooctye

Zona pellucida

• Glycoprotein layer Fertilisation (sperm binding)

Cell membrane - Control entry of sperm

First polar body - small haploid extra chromosomes

Secondary oocyte arrested at metaphase 2

Fertilisation definition

Fusion of haploid nuclei of sperm and secondary oocyte to form diploid zygote

Occur in oviduct

Cortical reaction

Triggered by sperm entry

Cortical granules release enzymes

Zona pellucida modified →fertilisation membrane

Prevent polyspermy

Acrosome reaction

Sperm contact zona pellucida

Acrosome release hydrolase enzymes

• Digest zona pellucia

• Allow sperm reach oocyte

Capacitation

Increase membrane permeability of sperm

Prepare sperm for acrosome reaction

Process of fertilisation

1. Sperm reach oviduct

Intercourse sperm vagina→ uterus → oviduct

2. Capacitation (sperm membrane more permeable)

3. Acrosome reaction (sperm contacr zona pellucida) release hydrolysing enzymes

4. Fusion of membrane sperm + secodnary oocyte → Sperm nucleus enter oocyte

5. Cortical reaction- cortical granules elease enzymes → fertilisation membrane

6. Complesion of meiosis 2n

• Ovum (egg)

• Second polar body

7. Female + male nucleus → diploid zygote

Implantation

Blastocyst embeds into endometrium of uterus

• Attach to endometrium

• Embed to uterine lining

Endometrium must be thickened maintained by progesterone

Implantation stages

1. Cleavage (mitosis)

After fertilisation zygote divide repeatedly by mitosis → ball of cells

2. Formation of blastocyst → hollow ball of cells inner cell mass (future embryo

3. Blastocyst move oviduct → uterus

4. Implantation attach endometrium thicken

5. Placenta formation

• Maternal tissue (endometrium)

• Foetal tissue (bastocyst)

Placenta formation and fucntion

• Maternal tissue (endometrium)

• Foetal tissue (blastocyst)

Exchange nutrients, oxygen and waste

Primary oocyte before puberty

Begin meiosis 1

Arrested in prophase 1

Remain dormant until puberty

Difference between primary and secondary oocytes

Primary

• Diploid

• Arrested in prophase 1

• Large

Secondary

• Haploid

• Arrested in metaphase 2

• Small surround by polar body and corona radiata

What happens during ovulation?

• Secondary oocyte is released from Graafian follicle

• Moves into fallopian tube (oviduct)

• First polar body may remain outside or nearby

• Follicle develops into corpus luteum

Structure associated with secondary oocyte after ovulation

Corona radiata - Granulosa cells nourish oocyte

Zona pellucida - Glycoprotein layer sperm binding prevent polyspermy

First polar body - Contain extra chromosomes meiosis 1

Cortical granules - Fuse membrane after sperm entry - modify zona pellucida

Cell membrane chromosomes - Secondary oocyte arrested metaphase 2 spindle hold chromosomes for completion of fertilisation

4 Hormones controling menstrual cycle

FSH (follicle stimulating hormone)

LSH (luteinising hormone)

Oestrogen

Progesterone

Stages of menstruation

1. Menstruation

• Low oestrogen + progesterone

• Endometrium breaks down

2. Follicular FSH released from anterior pituitary stimulate

• Maturation follicle secrete oestrogen

3. Oestrogen rise

• Repair endometrium

• Inhibit FSH + Stimulate LH

4. LH surge → Ovulation

• Follicle → corpus luteum

5. Progesterone - from corpus luteum maintain endometrium

• Inhibit FSH + LH

Menstruation if no fertilisation occur

Corpus luteum breaks down

Progesterone fall

Endometrium breaks down

FSH

Anterior pituitary

Stimulates follicle development

Forms theca → oestrogen

LH

Anterior pituitary

Cause graafian follicle

Pregnancy hCG

Human chorionic Gonadtrophin

• Secreted by embryo

• Maintain corpus luteum

What happens due to maintaining corpus luteum

Progesterone level stay high

Endometrium maintained

No menstruation

Birth hormone

Oxytocin released by posterior pituitary

• Stimulate uterine contractions

Positive feedback of oxytocin

Contractions→ More oxytocin → stronger contractions

Lactation

Prolactin

• From anterior pituitary

• Stimulate milk production

Oxytocin

• cause milk ejection

Early pregnancy

Embryo secrete hCG

hCG maintain corpus luteum

Corpus luteum → continue secrete progesterone

Later pregnancy hormones

Placenta secretes proesterogen + oestrogen

High concentrations

Progesterone

Maintain endometrium

Inhibit uterine contractions

Inhibit FSH LH

Oestrogen

Stimulate growth of uterus

Stimulate development of mammary glands

Labour hormonal cahnges

Oestrogen increase

Progesterone decrease

• allow uterus to contract

Oxytocin

• Posterior pituitary → uterine contractions

Prolactin

• Anterior pituitary

• Stimulate milk production

Structures and adaptions of placenta

Chorionic villi

• Finger like projections

• Contain foetal capillaries

• Increase surface area

Intervillous spaces

• Fill with maternal blood

Blood vessels

• Umbilical artery → foetus → placenta

• Umbilical vein → placenta → foetus

Counter-current flow

Maternal and foetal blood opposite directions

Maintain steep concentration gradient

Functions of placenta

Exchange

• Oxygen glucose → foetus

• Carbon dioxide urea → mother

Barrier

• Prevent blood mix

• Protect pressure difference

Hormone production

• Secrete hCG progesterone and oestrogen

Amniotic fluid

Acts as shock absorber

Protect foetus from damage0

Oestrogen to oxytocin

Oestrogen stimulates oxytocin receptors on uterus make contractions more effective