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Question
The lens is clear with no blood because it is made of dead cells.
Answer
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The Leydig cells of the testes constitute a blood-testis barrier that prevents autoimmune destruction of the sperm.
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Secretion of LH is inhibited by
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B. rapidly rising concentrations of estradiol.
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Which of the following is a precursor to melatonin synthesis?
A. tryptophan
B. serotonin
C. tyrosine
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B. regression of the wolffian ducts during embryonic development.
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The role of melatonin in puberty of humans is well established and critical.
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Pubic and axillary hair growth at puberty is from increased secretion of
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Epiphyseal growth in males is stimulated by estrogen.
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The rate at which GnRH is secreted from the hypothalamus determines whether LH or FSH is secreted from the anterior pituitary.
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A male with 5 alpha-reductase deficiency will have male internal sex organs but more female appearing external genitals.
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Males lacking testosterone receptors would
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Treating a male fetus with antibodies to DHT would prevent development of the epididymides.
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Female accessory sex organs develop from the mesonephric ducts.
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How many chromosomes are found in a normal human cell?
A. 23
B. 23 pair
C. 46
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Cryptorchid males do not produce testosterone.
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Epigenetic changes can not be passed on to a zygote.
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The stimulus of sucking causes release of prolactin-releasing hormone via a neuroendocrine reflex.
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Infants that are breastfed receive which of the following from the mother?
A. IgA
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What hormone is secreted by the anterior pituitary that stimulates production of milk proteins?
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Genetic screening of newborns using only a drop of blood can determine which of the following genetic disorders?
A. hypothyroidism
B. cystic fibrosis
C. sickle cell anemia
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What hormone may play a role in reducing the size of the uterus following delivery?
A. progesterone
B. prostaglandin
C. oxytocin
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DHEAS travels from the fetal adrenal cortex to the placenta where it is converted into oxytocin.
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Cortisol from the fetal adrenal gland will stimulate maturation of the lungs and production of surfactant.
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Blood within the umbilical ___________ contain(s) high concentrations of fetal waste products.
arteries
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A ball of about eight cells formed about 50 to 60 hours after fertilization is called a
A. zygote.
B. morula.
C. blastocyst.
D. embryo.
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The progressive fusion of the acrosomal membrane with the plasma membrane of the sperm is called the
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After meiosis I in males, ________ are formed.
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B. decreased, K+
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D. decreased, Na+
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Cells synthesizing hydroxyapatite in bones are termed as
A. osteoblasts.
B. osteoclasts.
C. osteocytes.
D. osteosarcoma cells.
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Bone resorption is produced by the action of _____________, which return bone calcium and phosphate to the blood.
A. osteoblasts
B. osteoclasts
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