Human Reproduction🍼

Gonad

An animal organ that produces sex cells

Testes

The male gonads

Temperature of testes

Must be maintained at 35°C for meiosis

Location of testes

Outside the body cavity in the scrotum

Function of testes

Produce sperm and testosterone

Seminiferous tubules

Site of sperm production in the testes

Interstitial (Leydig) cells

Produce testosterone

Sperm cells

Haploid male gametes produced by meiosis

Chromosome number in sperm

23 chromosomes

When sperm production begins

At puberty

Acrosome

Contains digestive enzymes to penetrate the egg

Function of acrosome

Digests egg membrane

Midpiece (collar)

Contains many mitochondria for energy

Tail (flagellum)

Allows sperm movement

Survival of sperm

Up to 5–7 days in the female reproductive tract

Testosterone

Male sex hormone produced in testes

Function of testosterone

Causes primary and secondary sexual characteristics

FSH in males

Produced by pituitary; stimulates sperm production

LH in males

Produced by pituitary; stimulates testosterone production

Scrotum

Keeps testes at 35°C

Epididymis

Sperm mature and are stored here

Vas deferens (sperm duct)

Carries sperm to the urethra

Seminal vesicles

Produce sugary alkaline seminal fluid

Function of seminal fluid

1. Transport of sperm 2. Supplies fructose (sugar) to sperm 3. Neutralised acidity in urethra and acidity in vagina.

Prostate gland

Adds milky nourishing fluid to semen

Cowper’s gland

Produces alkaline fluid that neutralises urine in urethra

Urethra

Carries sperm and urine out of the body

Penis

Transfers sperm to the vagina

Semen

A mixture of sperm and seminal fluids

Primary sexual characteristics

Sex organs and associated glands

Secondary sexual characteristics

Features that distinguish males and females at puberty

Male secondary sexual characteristics

Facial/pubic hair, deep voice, broad shoulders, oily skin

Female secondary sexual characteristics

Breast development, wider hips, increased body fat

Menstrual cycle

Series of changes every ~28 days if no fertilisation occurs

Length of menstrual cycle

21–40 days

Menopause

End of menstruation (usually ages 45–55)

Fertile period

Time when fertilisation is most likely (days 7–16)

Ovary

Produces eggs and female hormones

Fallopian tube

Carries egg to uterus; site of fertilisation

Uterus (womb)

Site of implantation and embryo development

Endometrium

Lining of uterus that nourishes embryo

Cervix

Opening between uterus and vagina

Function of cervix mucus plug

Prevents infection; dissolves during fertile period

Vagina

Receives penis; birth canal; acidic to prevent infection

Ovulation

Release of an egg from the ovary

Sexual arousal

Penis becomes erect; vagina lubricates

Copulation

Sexual intercourse

Orgasm

Climax of sexual excitement

Ejaculation

Release of semen from the penis

Insemination

Release of semen into the vagina

Fertilisation

Fusion of sperm nucleus with egg nucleus to form a diploid zygote

Chromosome number after fertilisation

46 (diploid)

Site of fertilisation

Fallopian tube

Role of acrosome enzymes

Open egg membrane

Block to polyspermy

Egg membrane changes to prevent other sperm entering

Mitochondrial DNA

Inherited only from the mother

Chemotaxis

Chemical attraction of sperm to egg from a chemical released by the egg, resulting in fertilisation.

Fertile period the time at which pregnancy is most likely to occur

Male infertility

Inability to produce viable sperm

Cause of male infertility

Low sperm count due to smoking, drugs, alcohol, stress

Treatment for male infertility

Lifestyle changes

Female infertility

Inability to conceive

Cause of female infertility

Failure to ovulate

Treatment for female infertility

Hormone therapy (e.g. FSH)

Implantation

Embedding of embryo into endometrium

When implantation occurs

6–9 days after fertilisation

Amnion

Membrane that forms around embryo

Amniotic fluid

Protects embryo; shock absorber

hCG hormone

Prevents breakdown of corpus luteum

Effect of hCG

Progesterone continues; menstruation stops

Placenta

Temporary organ formed from mother and embryo

When placenta fully functional

After 12 weeks

Blood mixing

Mother’s and foetus’ blood do not mix

Placenta functions

Exchange of materials between mother and foetus

Materials to foetus

Oxygen, nutrients, antibodies

Materials from foetus

Carbon dioxide, urea

Umbilical cord

Connects foetus to placenta

Umbilical vein

Carries blood to the foetus

Umbilical artery

Carries blood away from foetus

Zygote

Diploid cell formed after fertilisation

Morula

Solid ball of cells formed by mitosis

Blastocyst

Hollow ball of cells formed from morula

Trophoblast

Outer layer; forms placenta and membranes

Inner cell mass

Forms the embryo

Germ layers

Layers of cells that form all tissues

Ectoderm

Nervous system and skin

Mesoderm

Muscles, skeleton, circulatory system, kidneys

Endoderm

Digestive system, liver, pancreas

Gestation

Time from fertilisation to birth (38 weeks)

Week 4

Heart forms and beats

Week 5

Internal organs forming

Week 6

Eyes, ears, nose visible