Womens bodies: Anatomy

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Womens bodies Anatomy

• Topics skeletal anatomy, fat distribution,
  reproductive organs, mammary glands
• males females identical in most respects
• most diffs. are average diffs. with overlapping
  distributions
• skeletal anatomy exhibits gender differences
  (5/206 bones)

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Female skeleton

• 5 bones are unique 3 in head, 2 in pelvis
• skull bone diffs.
• mandible larger in males
• temporal bone has larger opening in males
• frontal bone larger in males
• diffs. in pelvis (ossa coxae)
• broader, flatter in females
• rounder pelvic inlet

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Female pelvis

• os coxa made of 3 smaller, fused bones
• illium (joined to sacrum)
• ischium
• pubis (joined by pubic symphysis)
• pubic symph. and sacroiliac joints are immobile
  except during pregnancy, childbirth
• pelvic inlet is round (vs. elongated oval)
• men have 32 more bone mass (due to density,
  diameter)
• on average, men have longer arms and legs
  relative to body size
• women have greater pelvic tilt, smaller Q angle

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Body composition

• men have more muscle, women more fat
• results from diff. sex hormone ratios
• Sex hormones cause secondary sex characteristics
• Female sex hormones estrogens
• Estradiol
• Estrone
• Estriol
• Male sex hormones androgens
• Dihydrotestosterone (DHT)
• Testosterone
• androstenedione

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Sex hormones

• Sex hormones made from cholesterol (steroids)
• Chemical properties allow them to act inside cell
• Act through nuclear receptors (Fig. 3-3)

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Testosterone effects on fat storage

• in muscle cells, increases production of proteins
  that trigger cell growth, multiplication
• in adipocytes, increases production of proteins
  that cause lipid breakdown
• also changes cell membranes, limiting amount of
  lipid they take from bloodstream

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Body composition, contd.

• estrogen downregulates androgen receptors in fat
  cells
• decreased rate of lipid degradation
• high uptake of lipids
• effects of T high fat diet in men
  arteriosclerosis
• also accounts in part for increased incidence of
  heart disease in postmenopausal women
• sex hormones affect fat storage patterns
• high E, low T gt stored in alpha adipocytes
  (extremities)
• low E, high T gt stored in beta ad. (abdomen)

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Physiological effects of body composition

• women have higher fat muscle ratio (.42 vs.
  .24)
• men have more blood vessels for their size,
  greater blood volume, bigger heart, more
  hemoglobin
• explains diffs. in athletic performances
• other roles of fat
• cushions internal organs
• insulation
• stores fat-soluble vitamins, energy

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Reproductive anatomy Breasts

• specialized skin glands (modified sweat glands)
• found in mammals
• found in both sexes nonfunctional in males
• develop in response to estrogen at puberty
• lobules
• made of alveoli (sacs), ducts
• milk production occurs in sacs
• each alveolus empties into lactiferous duct gt
  lactiferous sinus gt through nipple

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Breasts, contd.

• alveoli
• epithelial cells (milk-producing)
• myoepithelial cells (milk-ejecting)
• lobules are separated, supported by connective
  tissue fat
• all women have same amount of mammary tissue
• size, lumpiness varies with menstrual cycle
• cyclic changes promote growth of benign cysts or
  fibroid tumors
• 70-90 of women experience fibrocystic changes in
  their breasts

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External genitals

• called pudendum (pudere, to be ashamed)
• includes vulva, clitoris
• vulva 2 sets of labia
• labia majora
• labia minora (no fat or hair hood of clitoris)
• role protection sexual arousal
• contain sebaceous glands
• role of sebum repels urine, menstrual blood,
  bacteria

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Clitoris

• arises from genital tubercle
• sole function sexual arousal, orgasm
• generous blood, nerve supply
• becomes erect due to vasocongestion
• during orgasm, congestion relieved rhythmic
  contractions of surrounding muscles
• below clitoris opening to urethra (passageway
  for urine to exit bladder)
• below urethra vaginal opening, surrounded by
  membranous fold (hymen)

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Internal genitals vagina

• muscular organ connected to uterus
• passageway with potential space
• inner surface hairless skin and glands
• mechanisms for preventing infection
• outer layers of skin shed, broken down
• flow of cervical mucus
• vaginal lubrication by vestibular glands (at
  entrance)
• water released by surface blood vessels

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Vaginal flora

• discharge fed upon by good bacteria
  (lactobacilli)
• produce lactic acid
• acidic environ. keeps yeast in check
• decrease in lactobacilli gt yeast infections
• contributing factors
• antibiotics
• pregnancy
• suppressed immune system (stress, AIDS)
• soaps, toilet paper dyes, perfumes
• douching

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Uterus

• at 90 degree angle to vagina
• lies on top of bladder in most women (80)
• others gt on top of rectum (tipped uterus)
• exposure to DES during development can lead to
  T-shaped uterus gt compromises fertility
• size of fist in nonpregnant state
• wall is 1 cm thick perimetrium, myometrium,
  endometrium
• lower region cervix opening os
• childbirth changes os (dot to dash)
• dilates slightly during orgasm and 30 min.
  following

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Oviducts

• extension of top of uterus
• not attached to ovaries
• fimbria and suction direct movement of eggs
• suction due to movement of cilia
• blockage
• increased risk of tubal pregnancy
• impairment of fertility
• women have risk of peritonitis due to opening of
  oviducts into abdomen

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Ovaries

• at birth, 1-2 million germ cells present
• lost progressively throughout life (99 never
  ovulate)
• 1 eggs ovulated per month
• eggs surrounded by follicles
• after ovulation, follicle becomes corpus luteum
• secretes estrogen, progesterone
• prepares body for pregnancy
• functional cysts can develop