Puberty & Spermatogenesis (3) Flashcards
The process of physical andphysiological changes is called puberty. It leads to:
• the development of secondary sex characteristics. • an immature individual (child) becoming capable of reproduction.
The age at which puberty begins is mainly affected by ____ factors. In girls, puberty occurs between the ages of ___ and ___, and in boys between the ages of ___ and ___.
genetic 11 and 14 14 and 16
However, in ___ climates, puberty can start earlier while in ___ climates, one or two years later.
warmer cooler
What is adolescence?
This period of physical, physiological as well as psychological change is known as adolescence. It extends from the start of puberty for a number of years, e.g. until the age of 17 to 20 (females) and 18 to 21 years (males).
How does puberty start? (3)
• The pituitary gland, under stimulation from the hypothalamus, releases gonadotropins (hormones that stimulate the gonads), which initiate puberty. −In males, interstitial-cell-stimulating hormone (ICSH) stimulates the testis to secrete testosterone. −In females, follicle-stimulating hormone (FSH) stimulates the ovaries to produce oestrogen. • Testosterone and oestrogen then initiate changes to the gonads and to other parts of the body. •. The results of changes to the gonads are called primary sexual characteristics as they influence the process of reproduction. Other physical changes are referred to as secondary sexual characteristics as they have nothing to do with the actual reproductive process.
What physical changes occur during puberty in girls? (11)
• breast development; normally the first sign of puberty starts between 10 and 12 years old. • growth of hair in the pubic area and armpits, at about 11-12 years, is often the second noticeable change. • increase in size of uterus, ovaries and the primary follicles. • widening of pelvis and thus the hips, to provide a wider birth canal. • deposition of fat on hips, thighs, upper arms and buttocks. • start of the 28-day menstrual cycle. The average age of starting is between 12 and 18 years. • the first menstrual bleeding, referred to as menarche. It typically occurs about two years after breast development starts. • menstruation is unique to humans and close primate relatives such as chimpanzees. • ovulation, which in about 80% of girls only occurs after the first year of menstruating. • growth spurt lasting two to three years occurs. •possible acne as the skin gets oilier.
What physical changes occur during puberty in boys? (8)
• enlargement of testis and penis, usually the first sign of puberty. Maximum size is reached about 6 years after the onset of puberty. • hair growth in the pubic area and armpits, at about 13 to 14 years; facial hair grows later. • increase in size of larynx (voice box) and thickening of the vocal cords, which causes the voice to deepen. • enlargement of skeletal muscles and broadening of shoulders. By the end of puberty the bones are heavier and muscle mass is nearly double. • sperm production begins. • growth spurt of two to three years occurs. Ever wondered why teenage boys eat so much? • acne can occur; it is more common in boys than girls. It cannot be prevented or easily reduced, but usually disappears at the end of puberty.
What are the distinctive human sexual activities? (3)
•Human males are sexually fertile all the time; males of most mammalian species are not. • Menstruation is unique to humans and close primate relatives such as chimpanzees. The females of other placental mammal species have oestrous cycles, in which the animal reabsorbs the endometrium if fertilisation does not occur during that cycle. • Mating in humans and to a lesser degree in most other higher primates is not confined to the period when ovulation occurs. This mating is designed to reinforce pair-bonding; especially necessary where care of the young is prolonged as in humans.
Define Oestrous.
Oestrous = a time when females ovulate and can be impregnated
Define Nocturnal emission.
Nocturnal emissions(‘wet dreams’)occur in celibate males. celibate = abstaining from sex
What is Gametogenesis?
Gametogenesis is the formation of maturegametes (sperm and eggs) by the reproductive glands (gonads).
Does gametogenesis involve meiosis or mitosis?
It involves meiosis, a unique kind of nuclear division, which results in a halving of the number of chromosomes: from 46 (in body cells) to 23 (in gametes). This is to ensure that on fertilisation, the number of chromosomes returns to 46 in the fertilised egg (zygote).
What is Spermatogenesis?
Spermatogenesis is the sequence of events during which mature, haploid sperm are producedfrom the germinal epithelium in the seminiferous tubules of the testis. The hormone, testosterone, is essential for the making of sperm.
What are the four phases of spermatogenesis?
- Multiplying phase - Growth phase - Reduction phase - Differentiation phase
What does the multiplying phase entail?
The diploid (2n) spermatogonia (germ cells) of the germinal epithelium divide repeatedly by mitosis to form new spermatogonia (2n).
Diagram of a sperm cell.
