PUBERTY 2.ppt - Puberty-midlife changes LEARNING OUTCOMES At the end of the topics students should be able:to Define pubertyIdentify factors regulating

PUBERTY 2.ppt - Puberty-midlife changes LEARNING OUTCOMES...

This preview shows page 1 out of 63 pages.

You've reached the end of your free preview.

Want to read all 63 pages?

Unformatted text preview: Puberty -midlife - changes LEARNING OUTCOMES At the end of the topics students should be able :to Define pubertyIdentify factors regulating pubertyState the stages of pubertyCompare secondary sexualcharacteristics between males and females Relate hormonal levels with stages andcharacteristics of puberty Entry questions ?What is puberty. 1 What factors that influence puberty in male and. 2 ?female Is there a relationship between melatonin and. 3 ? growth hormone with puberty Sketch the general hormonal profiles during pre-. 4 . and post-puberty ?What are the endocrine glands involved. 5 Compare stages of puberty and structural . 6 changes between males and females ? What are the related abnormalities in puberty. 7 Puberty is the stage of physical maturation in which an individual becomes physiologically capable of sexual reproduction. • the physical and biochemical changes •maturation of the hypothalamic/pituitary/gonadal axis •development of secondary sex characteristics and reproductive function •co-ordinated consequences of adrenarche and gonadarche •androgens by the adrenal gland •sex steroids by the testis or the ovary related to stimulation by gonadotropins -the transition between the juvenile state and the mature reproductive state when secondary sex characteristics develop and fertility is achieved -initiation is adrenarche (DHEA and DHEAS ) in both male and female Fetal Life In males, the earliest secretion of testosterone at 7 to 8 weeks gestation occurs independent of gonadotropin and continues with stimulation of . hCG The hypothalamic/pituitary axis completes .development at about 20 weeks gestation Gonadotropins become sensitive to estrogen feedback suppression (neg. feedback) and fall to undetectable levels Childhood ) The period between infancy and puberty (juvenile very low levels of gonadotropins and gonadal steroids suggesting a profound suppression of thehypothalamic GnRH center by steroids PHYSIOLOGY OF PUBERTY The biological changes include: •neurosecretory factors and/or hormones •somatic growth-adolescent growth spurt (45% of the adult skeletal mass acquired between age 11 and age 18), -end of puberty, the average male has 56% more muscle mass than the average female. •development of the sex glands PHYSICAL CHANGES OF PUBERTY •Female secondary sex characteristics •Male secondary sex characteristics PUBERTY It is a physiological phase lasting 2 to 5 years, during which the organs mature Onset of Puberty FSH and LH (gonadotropins) secretion is high in newborn, but then falls to low levels in . few weeks )At puberty: (75% Drop of melatonin .Brain maturation increases GnRH secretion Decreased sensitivity of gonadotropin to negative feedback of estrogens During late puberty, pulsatile secretion of LH and .FSH increase during sleep .Stimulate a rise in sex steroid secretion - Onset of Puberty ) Rise in testosterone and .estradiol-17 Produce secondary .sexual characteristics Age of onset related to the % of body fat and physical activity in the female Leptin secretion from adipocytes may be required for puberty stimulate GnRH(- trigger neuroendocrine cascade resulting in early .menarche (continued Insert fig. 20.10 PHYSIOLOGY OF PUBERTY •Activation of the hypothalamic-pituitary-gonadal axis: -Induces and enhances the progressive ovarian and testicular sex hormone secretion -Responsible for the profound biological, morphological, and psychological changes to which the adolescent is subjected Sex steroid production: -appearance and maintenance of sexual characteristics -Capacity for reproduction PHYSICAL CHANGES OF PUBERTY Puberty proceeds through five stages from childhood to full maturity (P1 to P5) as described by Marshall and Tanner. In both sexes, these stages reflect the progressive modifications of the external genitalia and of sexual hair. Secondary sex characteristics appear at a mean age of 10.5 years in girls and 11.5 to 12 years in boys. PUBERTAL STAGES (TANNER) FEMALE P1 - Prepubertal P2 - Early development of subareolar breast bud +/-small amounts of pubic hair and auxiliary hair P3 - Increase in size of breast tissue and areolae, increased amount of dark pubic hair and of auxiliary hair P4- Further increase in breast size and areolae, adult pubic hair P5 - Adult stage, pubic hair with extension to upper thigh Manifestations of puberty : in the female include 1. 2. 3. 4. Menarche Appearance of secondary sex characters Physical development Psychological changes Secondary sex characters :include And development of the breast, appearance of pubic and auxiliary hair. The first sign of pubertal development is usually breast growth (thelarche), followed by appearance of pubic hair (pubarche), then (auxiliary hairadrenarche), then (menarche). The mean interval between breast budding and menarche is 2.5 years with a standard deviation of about one year. Adrenarche means increased activity of the supradrenal cortex at puberty with increased production of adrenal androgens which lead to appearance of pubic and axillary hair. The anterior pituitary responds by progressive secretion of FSH and LH associated with increased secretion of growth hormone . The ovaries respond to the increase in Gonadotrophin secretion by follicular development & estrogen secretion . Estrogen causes development of the genital organs and the appearance of the secondary sexual characters . With increased estrogen secretion , menarche and cyclic estrogen secretion occurs . OVARIAN DEVELOPMENT: In prepuberty, the ovarian size volume extends from 0.3 to 0.9cm3. More than 1.0 cm3 indicates that puberty has begun. During puberty, the ovarian size increases rapidly to a mean postpubertal volume of 4.0 cm3 (1.8 to 5.3 cm3). OVARIAN DEVELOPMENT: The rising levels of plasma gonadotropins stimulate the ovary to produce increasing amounts of estradiol. Estradiol is responsible for the development of secondary sexual characteristics, that is, growth and development of the breasts and reproductive organs, fat redistribution (hips, breasts), and bone maturation. The maturation of the ovary at adolescence correlates well with estradiol secretion and the stages of puberty. UTERINE DEVELOPMENT The prepubertal uterus is tear-drop shaped, with the neck and isthmus accounting for up to two-thirds of the uterine volume; then, with the production of estrogens, it becomes pear shaped, with the uterine body increasing in length and thickness proportionately more than the cervix. Genital organs :changes Uterus: enlarge, Uterus / Cervix :2 / 1 Ovaries: 1. Increase in size, almond shape 2. 300 thousands primary follicle at menarche ( 2 million at birth) Genital organs :changes Mons pubes, labia majora & minora: increase in size. Vagina: 1. 2. 3. length: increase, appearance of the rugae Epithelium: thick, stratified squamous., containing glycogen pH: acidic. :Cause of puberty During childhood , the hypothalamus is extremely sensitive to the negative feedback exerted by the small quantities of estradiol & testosterone produced by the child's ovaries . As puberty approaches , the sensitivity of the hypothalamus is decreased and subsequently , it increases the pulsatile GnRH secretion . Factors affecting the initiation of pubertal :development 1 - Height and weight ratio (nutritional factors). 2 - Maturation of the hypothalamus . 3 - Increased neurotransmitter output in CNS . 4 - Onset of adrenal androgen activity :Deposition of SC fat 17% to menstruate & 22% to ovulate MENARCHE During puberty, plasma estradiol levels fluctuate widely, probably reflecting successive waves of follicular development that fail to reach the ovulatory stage. The uterine endometrium is affected by these changes and undergoes cycles of proliferation and regression, until a point is reached when substantial growth occurs so that withdrawal of estrogen results in the first menstruation (menarche) OVULATION Plasma testosterone level also increases at puberty although not as markedly as in males. Plasma progesterone remains at low levels even if secondary sexual characteristics have appeared. A rise in progesterone after menarche is, in general, indicative that ovulation has occurred. The first ovulation does not take place until 6-9 months after menarche because the positive feedback mechanism of estrogen is not developed. (E2 LH) PUBERTAL STAGES (TANNER) MALE P1- Prepubertal, testicular length less than 2.5cm P2 - Early increase in testicular size, scrotum slightly pigmented and dark pubic hair P3 - Testicular length 3.3-4 cm, lengthening of the penis, increase in pubic hair P4 - Testicular length 4.1-4.5cm, increase in length and thickening of the penis, adult amount of pubic hair P5 - Testicular length greater than 4.5cm, full spermatogenesis Secondary sexual development in boys: •growth are enhanced maximum rate is attained around 14 to 15 years of age •testis increases in size, mainly at the expense of the seminiferous tubules •testicular volume of 4 ml or a longitudinal diameter greater than or equal to 2.5 cm and a slight progressive increase in scrotal folds and pigmentation constitute the first signs of puberty •the interstitial (Leydig) cells develop and ensure synthesis and secretion of testosterone •Puberty results from the development of the seminiferous tubules under the stimulating effect of FSH. TESTES DEVELOPMENT: LH secretion induces the differentiation of interstitial cells into testosterone-secreting Leydig cells, which, in turn, exert a negative feedback control on LH secretion. As puberty progresses, spermatogenesis is initiated and then sustained by FSH and by testosterone produced by the Leydig cells under LH control. TESTES DEVELOPMENT: A significant increase of plasma testosterone is found only between Tanner pubertal stages P3 and P4. Dihydrotestosterone shows a pattern similar to that of testosterone, and the proportion of dihydrotestosterone to testosterone decreases gradually until adulthood, when dihydrotestosterone levels are approximately 10% of those of testosterone. : REF Neinstein. 1 LS and Kaufman FR, chapter 1: Normal Physical Growth and Development from Neinstein .L.S Adolescent. 2 Health Care: A Practical Guide, 4th edition, Lippincott Williams and Wilkins 2002 THIGH: BODY LENGTH PUBERTAL GROWTH SPURT Solidification of the epiphyseal plate and the growth stops HYPOTHALAMOPITUITARY-GONADAL AXIS Endocrine Function of the Testes Testosterone and its derivatives are responsible for initiation and maintenance of body changes in .puberty Stimulate growth of muscles, larynx, and bone growth until sealing of the .epiphyseal discs Insert fig. 20.15 Promote hemoglobin .synthesis Responsible for .spermatogenesis Estrogen Secretion Sertoli and Leydig cells secrete small .amounts of estradiol : May be responsible for.Negative feedback in brain .Sealing of epiphyseal plates Regulatory function in fertility HYPOTHALAMOPITUITARY-GONADAL AXIS :Skin .Skin becomes more oily• .Body will sweat more• Acne or pimples may• develop Source: American Academy of Pediatrics: Puberty Information for .Boys and Girls /puberty.htm :Menstruation or period Begins for most girls• between the ages of 9 .and 16 .Occurs monthly• Most periods last from 3• .to 7 days May feel discomfort• before, during, or after a period Breasts grow in size and .shape Breast growth is often• the first area of growth during puberty :Hair Hair grows under the• arms, legs, and in the pubic area (between ).legs Hair growth begins• shortly after breast .development :Body Shape .Hips get wider• .Waist gets smaller• Body will build up fat in• ,the stomach, buttocks .and legs Body develops a more• curved shape :Body Size Arms, legs, hands, and• feet may grow faster . than rest of body :Penis Penis and testicles get• .larger May experience more• erections (hardening of ).the penis Body will begin to• produce sperm during puberty :Voice :Body Shape .Voice gets deeper• Grow taller and• Voice may start• .shoulders grow broader cracking for a period of .Muscles get bigger• time Gain more weight• :Hair Chest hair may appear• in some during puberty ).or years later( If breast development, pubic and/or axillary hair, and menses occur earlier than normal variations from the mean, the terms premature thelarche, pubarche and/or adrenarche, and menarche are used. Abnormalities of puberty 1 - Precocious puberty . 2 - Delayed puberty . Growth problems : during adolescence e.g. short stature or tall stature , marked obesity and menstrual disorders at puberty . Secondary sexual characters. Secondary characters in animals Secondary characters in fresh water fishes )Suhanas & Halawani (2005 ...
View Full Document

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

Stuck? We have tutors online 24/7 who can help you get unstuck.
A+ icon
Ask Expert Tutors You can ask You can ask You can ask (will expire )
Answers in as fast as 15 minutes