Chapter 26 - Sexual Reproduction In Humans Flashcards
Structure and function of scrotum
- Skin bag that holds the testes
2. Keeps temperature of testes 2*C lower than body temperature
Structure and function of epididymis
- Sperm passes from testes to epididymis which lies on top of the testis
- Sperm matures here and bacome mobile
- Store sperm
Sperm duct
- Transports sperm towards glands
Glands
- Add seminal fluid to give energy and prevent drying out
- Makes semen alkaline
- Called semen
Prostate gland
- Add seminal fluid
2. Helps with ejaculation
Urethra
- Through which semen and urine passes
Penis
- Organ inserted into vagina
2. Contains erectile tissue to make penis erect
Structure of spermatozoa
- Consist of head, middle and tail
- Head contains nucleus
- Nucleus is haploid
- Acrosome contains hydrolytic enzymes
- Contain mitochondria for energy
Formation of sperm
- Occurs in seminiferous tubules
- Tubules are specialised cells called germinal epithelium
- They divide by mitosis to form primary spermatocytes that are diploid
- Then form secondary spermatocytes that are haploid
- Then form spermatids which are haploid
- Then differentiate into spermatozoa
- This is called spermatogenesis
- Process controlled by testosterone and FSH
Structure and function of ovaries
- Store and releases matured ova
2. Produces oestrogen and progesterone
The fallopian tube
- Narrow tube through which ovum travels
2. Fertilisation occurs here
The uterus
- Muscular organ where egg develops
The cervix
- Narrow passage that leads from uterus to vagina
The vagina
- Muscular tube lined with thick mucous membrane
2. Receives the penis
Labia of vulva
- Outside the visible part
Structure of ovum
- Inside is the haploid nucleus
- Contains yolky cytoplasm as nourishment
- Surrounded by jelly coat to ensure only one sperm enters
Formation of ova
- Ovary covered by germinal epithelium
- Mitosis form many diploid primary oocytes
- Surrounded by follicles to form primary follicle
- During puberty meiosis form haploid secondary oocytes
- Each is in a graafian follicle
- The Graafian follicle burst open to release ovum
- Each month one develops into mature ovum
- Called oogenesis
Role of testosterone
- Transported in blood to different organs
- Causes voice to break
- Causes muscle enlargement
- Growth of pubic hair, facial hair and armpit hair
Role of oestrogen
- Form from the Graafian follicle and transported in the blood
- Causes sub deposition of subcutaneous fat
- Widening of the hips
- Hair under arm and pubic hair
- Breast develops
The menstrual cycle
- One cycle lasts 28 days
- Cycle controlled by hormones
- New cycle starts with period
- Menstruation lasts 4-5 days
- During menstruation hormones are low
- After periods the hormones rise
- By day 14 endometrium has thickened aNd ovulation occurs
- After ovulation hormones rise higher
FSH (follicle stimulating hormones)
- Produces by anterior lobe of pituitary gland
- Causes Graafian follicle to form mature ovum
- Stimulates Graafian follicle to produce oestrogen
- Rise after periods and peaks on day 14
Oestrogen
- Produced by Graafian follicle
- Causes endometrium to build up, repair and thicken the new uterus lining
- Stimulates pituitary gland to produce LH
- Peaks on day 11
LH (luteinizing hormone)
- Produced by anterior lobe of pituitary gland
- Causes ovulation
- Stimulates corpus luteum (Graafian becomes corpus luteum )
Progesterone
- Produced by corpus luteum
- Maintains the lining
- It thickens lining even more
- Inhibits production of FSH
- Fall in progesterone causes lining to break down
Role of oestrogen in pregnancy
- Prepares the uterus for labour by increasing sensitivity of muscle walls for contractions
- Causes lining to become thicker tougher and have better blood supply
Role of progesterone in pregnancy
- Ensure pregnancy is maintained
- High levels inhibit contractions of the uterus
- Prevent periods
- Prevent ls further ovulations
- Stimulates mammary glands
Sexual intercourse
- During sex the erect penis is inserted into the vagina
2. The Man expels semen by ejaculation
Fertilisation
- Sperm propels itself through the cervix up the uterus into the Fallopian tube
- When the sperm reaches the egg only one sperm can enter and loses its tail
- When the sperm enters the membrane surrounding the egg becomes impermeable
- When the two haploid a fuse fertilisation occurs
The process of implantation
- The zygote passes through Fallopian tube by means of cilia
- While zygote moves mitosis takes place forming the morula
- The morula continues to divide to form the blastocyst
- After 5-7 days the blastocyst reaches the uterus
- The blastocyst becomes the embryo
- The embryo sinks into the lining and embeds itself
The placenta
- The thickened lining where embryo embedded itself is called placenta
- Two arteries carry blood away and one vein to carry blood to
- Blood never mixes
The umbilical cord
- The two arteries and one vein and some connective tissue form umbilical cord
- Only connection between foetus and placenta
The amniotic fluid
Fluids that surrounds the foetus
The amniotic sac
Strong membrane that surrounds the foetus and keeps amniotic fluid inside
Fraternal twins
- Two egg cells are released from different ovaries
- Both get fertilised by different sperm
- Two embryos develop
Identical twins
- One egg is released and fertilised
- The embryo splits into two
- Both implant
Triplets
- Two egg cells released
- Fertilised by two sperms
- Ons embryo splits into two
- Three embryos implant into uterus
Function of placenta
- Acts as endocrine gland
- Oestrogen prepares womb for labour
- Progesterone maintains the uterus
- Exchange of substance
- Oxygen and nutrients diffuse across placenta
- Allows antibodies from mother
- Prevents blood mixing
- Prevents pathogen
Function of amniotic sac
- Prevents entry of pathogens
- Secrets amniotic fluid
- Covers entire foetus
Function of amniotic fluids
- Foetus floats in fluid
- Act as cushion against bumps
- Keeps baby in gravity free space
- Pressure free space
- Prevents drying out
Function of umbilical cord
- Connection between foetus and placenta
2. Carries blood to and from foetus
Effect of tobacco on foetus
- CO causes stunted growth
- CO binds with haemoglobin
- More susceptible to respiratory infections
Effects of nicotine
- Causes blood vessels to constrict
- Reduces oxygen transport
- Causes premature babies
- Increases risk of miscarriage
Effects if alcohol
- Causes fetal alcohol syndrome
- Brain is under developed
- Reduced growth
- Heart defects
- Causes cleft palates and hare lips
Effect of opiate drugs
- Cause addiction
2. Causes limb deformities
Nutrition of mother during pregnancy
- Balanced diet
- Sufficient protein
- Calcium
- Vitamin A, C, D
- Iron, phosphorus, fibre
Structure and function of testes
- Situated in scrotum
- Produces spermatozoa in the seminiferous tubules
- The interstital cells produces testosterone
Process of normal birth
- Few weeks before birth foetus turns upside down
- His head lies next to the cervix
- Contraction push foetus to cervix
- Cervix opening starts to dilate
- The contractions are now more forcefully and frequent
Process of Caesarian birth
- The baby is surgically removed from the womb
Advantages of breast feeding
- Most suitable food
- Always correct temperature
- Contains antibodies
- Always available
- Digested more easily
- Contains no additives
Contraception : chemical
- Contraceptive pills
- Spermicides cream
- Injection - the shot
Contraceptive : mechanical
- Female diaphragm
- Intra uterine device
- Male condom
- Female condom
Contraceptives : natural
- Rhythm method
2. Withdrawal method
Contraceptives : surgical
- Vasectomy
2. Tubal ligation