St A - Puberty and Lactation

Question 1

What does puberty involve?

Answer 1

Physiological processes of gonadarche (maturation of gonads by gonadotrohins) and adrenarche (increase in production of androgens (sex hormones) by adrenal cortex)

Question 2

What are the primary and secondary sexual characteristics?

Answer 2

Primary - formation of reproductive organs (present at birth)
Secondary - Develop during puberty but are not directly required for reproduction

Question 3

Define;

• Thelarche,
• Pubarche,
• Menarche,

Answer 3

• Thelarche - Onset of breast development.
• Pubarche - First appearance of pubic hair.
• Menarche - Onset of menstruation

Question 4

What is the hypothalamic-pituitary-adrenal axis?

Answer 4

Occurs at 6-8yeats and results in ACTH produced by pituitary. It causes stimulation of adrenal glands to secrete androgens (go on to cause pubarche, development of pilosebaceous units in skin and increases cortical bone density)

Question 5

Describe the stages of female puberty

Answer 5

Breast development - first sign and can occur from 8.5 to 12.5 years.
Pubic hair and rapid height growth (tends to occur almost immediately after breast development).
Menarche - average 13 years old, above 2.5 years after start of puberty and signals the end of growth.

Question 6

What are the hormone-dependant secondary sexual characteristics in girls?

Answer 6

• Facial, underarm and pubic hair,
• Thick secretions of skin oil glands,
• Female pattern of fat distribution,
• Hips and pelvis widen,
• Uterus and cervix enlarge, secretory function increases,
• Bone growth via hormone secretion then termination via closure of epiphyseal plates.

Question 7

What are the stages of male puberty

Answer 7

• Testicular enlargement (first sign occurring between 10-15).
• Pubic hair growth and penile growth (normally 2 years after hair growth)
• Spermarche (appearance of sperm in seminal fluid)
• Growth spurt (when testicular volume is 12-15mls)

Question 8

How is puberty initiated?

Answer 8

Sustained increase in pulsatile GnRH release due to a change in sensitivity of hypothalamic neurons. This occurs at night and leads to more pronounced gonadotrophin release

Question 9

Name some factors that contribute to early puberty

Answer 9

• Genetics,
• Social factors (lower social class and obesity),
• Geographical factors (closer to the equator, lower altitudes and urban),
• Environmental exposures (endocrine disrupting chemicals),
• Race (earlier onset in black patients)

Question 10

What are some of the benefits of breastfeeding for baby?

Answer 10

• Reduced incidence of GI, resp and middle ear infections,
• Decreased risk of childhood diabetes, asthma and eczema,
• Lower risk of lactose intolerance,
• Improved intellectual and motor development,
• Decreased risk of obesity,
• Reduced autoimmune disease,
• Reduced risk of sudden infant death syndrome

Question 11

What are the benefits of breastfeeding for mum?

Answer 11

• Promotes recovery from childbirth,
• Promotes return to normal body weight,
• Period of infertility,
• Reduced risk of postmenopausal breast cancer,
• Reduced risk of ovarian cancer,
• Improves bone mineralisation

Question 12

Explain the anatomy of the breast

Answer 12

• Nipple surrounded by pigmented skin called areola.
• Modified sebaceous glands empty via lactoferous sinuses which open up onto surface of nipple.
• Adipose tissue is dominant in non-lactating breast,
• Glandular tissue only fully develops during pregnancy

Question 13

Describe features of secretory alveoli

Answer 13

Milk producing cells which are stimulated by prolactin

Question 14

Describe features of each alveolus

Answer 14

Surrounded by myo-epithelial cells and stimulated by oxytocin

Question 15

Describe the 5 major routes for milk production

Answer 15

1) Secretory pathways,
2) Transcellular endo/exo-cytosis,
3) Lipid pathways,
4) Transcellular salt and water transport through channels and transporters,
5) Paracellular pathway for ions and water

Question 16

Describe the development of the breasts till puberty

Answer 16

Birth - breast consists of lactiferous ducts without alveoli.
Puberty - Due to oestrogen, ducts develop and alveoli form at end of branches,
Each cycle - Proliferative changes in alveoli and potential secretory action.

Question 17

What are the changes to the breasts that occur during pregnancy?

Answer 17

Due to oestrogen, progesterone and prolactin, the glandular portion undergoes hypertrophy (replacing adipose tissue). From week 16 the breast is fully developed but is quiescent awaiting activation. After parturition, due to a drop in oestrogen and progesterone the breast produced colostrum before mature milk production begins

Question 18

Explain the suckling reflex

Answer 18

Suckling stimulus inhibits the hypothalamic release of dopamine which is the prolactin inhibitory factor. Prolactin is therefore released in proportion to strength and duration of suckling.

Question 19

Explain the milk ejection reflex

Answer 19

Suckling stimulates neurons in the hypothalamus to synthesis oxytocin (carried to posterior pituitary). The release of oxytocin into bloodstream acts on myo-epithelial cells in alveoli to contract and eject milk. It can occur in response to babies cry and inhibited by catecholamines.

Question 20

How is lactation inhibited during pregnacny

Answer 20

Prolactin is secreted during pregnancy but its action is inhibited by the high levels of progesterone, oestrogen and human placental lactogen. Steroid levels fall after birth and milk production begins.

Question 21

Explain how lactational amenorrhoea (LAM) occurs

Answer 21

Occurs in women who exclusively breastfeed. Prolactin supresses hypothalamic release of GnRH and therefore release of FSH and LH, this prevents follicular growth, ovulation and menstruation

Question 22

LAM is effective method of contraception so long as?

Answer 22

Must be amenorrhoeic, baby must be exclusively breastfed and baby must be less than 6 months old.