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MCAT BIOLOGY FLASHCARDS > MCAT BIO CH. 13 PART 1 > Flashcards

MCAT BIO CH. 13 PART 1 Flashcards

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1
Q

What is the role of the scrotum, in males?

A

Temperature regulation

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2
Q

Why are the testes located outside of the body, in males?

A

Sperm synthesis must occur at a few degrees below normal body temperature

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3
Q

What are the two roles of the testes, in males?

A
  1. Synthesis of sperm

2. Secretion of male sex hormones

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4
Q

What is an example of a male sex hormone, in males?

A

Androgen

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5
Q

What is the site of spermatogenesis, in males?

A

Seminiferous tubules

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6
Q

What are the walls of the seminiferous tubules made out of, in males?

A

Sustentacular cells - Sertoli cells

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7
Q

What is the general role of the sustentacular cells,in males?

A

Protect and nurture the developing sperm

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8
Q

The tissue between the seminiferous tubules is what, in males?

A

Testicular interstitium

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9
Q

What are interstitial cells and where are they found, in males?

A

Response for androgen synthesis and coated in testiular interstitium

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10
Q

What are Leydig cells, in males?

A

Interstitial cells

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11
Q

What are interstitial cells responsible for, in males?

A

For androgen (testosterone) synthesis

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12
Q

What does the seminiferous tubules empty into, in males?

A

The epididymis

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13
Q

What is the epididymis and where is it located, in males?

A

Located on the posterior of each testicle

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14
Q

What does the epididymis empty into, in males?

A

The ductus deferens

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15
Q

What is the ductus deference and what does it turn into, in males?

A

Vas deferens; leads to the urethra

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16
Q

To get to the urethra, the ductus deferens leaves what, in males?

A

Leaves the scrotum and enters the inguinal canal

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17
Q

What is the inguinal canal, in males?

A

The inguinal canal is a gunnel that travels along the body wall toward the crest of the hip bone

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18
Q

How many inguinal canal is there, in males?

A

Two; left and right

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19
Q

From the inguinal canal, the ductus deferens enters, in males?

A

Enters the pelvic cavity

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20
Q

What does the pelvic cavity join into and to form what, in males?

A

Joins the duct of the seminal vesicle to form the ejaculatory duct

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21
Q

What does the ejaculatory duct join from both sides of the body, in males?

A

The urethra

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22
Q

What is the seminal vesicles located, in males?

A

Posterior surface of the bladder

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23
Q

What do the seminal vesicle secrete and where, in males?

A

60% of the total volume of the semen into the ejaculatory duct

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24
Q

What glands produces semen, in males?

A

Seminal vesicles, prostate, and the bulbourethral glands

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25
Q

What is the use of semen for the sperm, in males?

A

Nourishing fluid for the sperm

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26
Q

What is the name for the three glands that produce semen, in males?

A

Accessory glands

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27
Q

What does the ejaculatory duct empties into, in males?

A

The urethra as it passes through the prostate gland

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28
Q

Where does the bulbourethral contribute to the semen production, in males?

A

Near the beginning of the urethra

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29
Q

What percentage of the total volume of semen does the prostrate gland contribute, in males?

A

35%

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30
Q

What is the purpose of the prostate gland, in males?

A

Nourishment and allow semen to coagulate after ejaculation

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31
Q

What percentage of the total volume of semen does the bulbourethral gland contribute, in males?

A

3%

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32
Q

What is the purpose of the bulbourethral gland, in males?

A

Lubricate urethra, neutralize acids in male urethra and female vagina

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33
Q

WWhat percentage of the total volume of semen does the testes contribute, in males?

A

2%

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34
Q

What is the purpose of the testes based on semen, in males?

A

Male gamete

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35
Q

What allows erection in the penis, in males?

A

Specialized erectile tissue

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36
Q

What is the erectile tissue composed of, in males?

A

Modified veins and capillaries surrounded by a connective tissue sheath

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37
Q

When does erection occur based on the erectile tissue’s functionality, in males?

A

When blood accumulates at high pressure in the erectile tissue

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38
Q

What are the there compartments the contain erectile tissue, in males?

A

Corpora cavernosa (two of these) and the corpus songiosum

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39
Q

What are the three stages of male sexual act, in males?

A

Arousal, orgasm and resolution

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40
Q

The three stages of the male sexual act, what are they controlled by, in males?

A

An integrating center in the spinal cord which responds to physical stimulation and input from the brain

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41
Q

How can the cerebral cortex affect the integrating enter, in males?

A

Activate or inhibit

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42
Q

What type of nervous system is arousal dependent on, in males?

A

Parasympathetic nervous input

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43
Q

What are the two stages of arousal, in males?

A

Erection and lubrication

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44
Q

Based on the two stages of arousal, what is erection, in males?

A

Dilation of arteries supplying the erectile tissue

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45
Q

What happens during erection when arteries begin to dilate, in males?

A

Causes swelling which in turn obstructs venous outflow

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46
Q

Based on the two stages of arousal, what is lubrication, in males?

A

The bulbourehtral glands secrete a viscous mucous which saves as a lubricant

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47
Q

What type of nervous system is lubrication dependent on, in males?

A

Parasympathetic system

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48
Q

Which nervous system is required to be stimulated for orgasm, in males?

A

The sympathetic nervous system

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49
Q

What are the two stages of orgasm stimulation from the sympathetic nervous system, in males?

A
  1. Emission

2. Ejaculation

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50
Q

What is emission, based on orgasm, in males?

A

Propulsion of sperm from the ductus deferens and semen from the accessory glands into the urethra

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51
Q

How does mission cause propulsion of sperm, in males?

A

By contractions of the smooth muscle surrounding these organs

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52
Q

What is emission followed by, in males?

A

Ejaculation

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53
Q

What happens during ejaculation in males?

A

Semen is propelled out of the urethra

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54
Q

In males, during ejaculation, semen is propelled out of the urethra by what?

A

By rhythmic contractions of muscles surrounding the base of the penis

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55
Q

What type of reaction is ejaculation considered?

A

Reflex reaction caused by the presence of semen in the urethra

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56
Q

What constitutes of the male orgasm?

A

Emission and ejaculation together

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57
Q

What is resolution based on male orgasm?

A

Return to a normal unstimulated state

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58
Q

What is resolution controlled by, based on male orgasm?

A

Sympathetic nervous system

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59
Q

What is resolution of male orgasm caused by?

A

Constricting the erectile arteries

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60
Q

What happens when the erectile arteries are constricted based on male orgasm?

A

Deceased blood flow to the erectile tissue and allows the veins to carry away the trapped blood

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61
Q

What is the difference between emission and ejaculation?

A

Emission: Movement of sperm and semen components into the urethra
Ejaculation: Movement of semen from the urethra out of the body

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62
Q

What processes in a human being involve meiosis?

A

Gametogenesis

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63
Q

What is produced through meiosis?

A

Haploid gamaetes

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64
Q

The gametes produced by male during meiosis are know as…?

A

Spermatozoa or sperm

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65
Q

The gametes produced by female during meiosis are know as…?

A

Ova or egg

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66
Q

What is the fusion of the egg and sperm called?

A

Syngamy

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67
Q

What is the result of syngamy?

A

Zygote

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68
Q

The female gamete contributes more of the genome of the zygote than the male. T/F

A

False: gametes produced by males and females contribute EQUALLY to the genome of the zygote

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69
Q

When does the gametes produced by males and females not contribute equally?

A

Special case of the two different sex chromosomes X and Y giving rise to male offspring

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70
Q

Although both gametes contribute equally to the genome…..finish the sentence

A

The egg provides every other part of the zygote since the only part of the sperm which enters the egg is haploid genome

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71
Q

What is sperm synthesis called?

A

Spermatogenesis

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72
Q

When does spermatogenesis begin?

A

At puberty and occurs in the testes throughout adult life

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73
Q

What is the site of spermatogenesis?

A

The seminiferous tubules

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74
Q

What aids the seminiferous tubules through spermatogenesis?

A

The sustentacular cells found in the wall of the seminiferous tubules

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75
Q

Where are immature sperm precursors found?

A

In the outer wall of the tubule

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76
Q

Where are matured spermatozoa deposited?

A

In the lumen

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77
Q

What happens to the sperm once they are deposited into the lumen?

A

Transported to the epididymis

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78
Q

What are the cells that give rise to the spermatogonia and the oogonia?

A

Germ cells

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79
Q

What is the purpose of the spermatogonium?

A

Mitosis, replicate DNA in S phase

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80
Q

What does the primary spermatocyte undergo?

A

Meiosis I

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81
Q

What does the secondary spermatocyte undergo?

A

Meiosis 2

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82
Q

What is the role of the spermatid?

A

Immature sperm; turn in spermatozoan

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83
Q

What is the role of the spermatozoan?

A

Finish maturing; in seminiferous tubule and in epididymis

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84
Q

The final stages of sperm maturation occurs where?

A

In the epididymis

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85
Q

The spermatozoan can utilize motility upon entry into the epididymis. T/F

A

False: incapable of motility

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86
Q

When do spermatozoan become fully capable of motility?

A

When they reach the ductus deferens

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87
Q

What is the benefit of spermatozoan being incapable of motility until ductus deferens?

A

Very low metabolic rate that allows them to conserve energy and remain fertile during storage in the ductus defense

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88
Q

How does the shape of the spermatid change in order to become a sperm?

A

Dna condenses, cytoplasm shrinks, head and tail of flagellum forms

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89
Q

What is located on the tail of the sperm?

A

Base of the tail contains many mitochondria

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90
Q

Where does the mitochondrial in the tail of the sperm get their energy?

A

From the fructose which the seminal vesicles contribute to the semen and from vaginal secretions

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91
Q

What is the acrosome?

A

A compartment on the head of the sperm that contains hydrolytic enzymes

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92
Q

Why do the acrosome contain hydrolytic enzymes?

A

Required for penetration of the ovum’s protective layer

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93
Q

What is bindin?

A

A protein on the sperm’s surface

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94
Q

What is bindin protein?

A

Attaches to receptors on the zona pellucida surrounding the ovum

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95
Q

What are the main hormones that help control spermatogenesis?

A
  1. Testosterone
  2. Luteinizing hormone
  3. Follicle stimulating hormone
  4. Inhibin
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96
Q

What is the role of testosterone in spermatogenesis?

A

Plays the essential role of stimulating division of spermatogonia

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97
Q

What is the role of luteinizing hormone in spermatogenesis?

A

Stimulates interstitial cells to secrete testosterone

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98
Q

What is the role of follicle stimulating hormone in spermatogenesis?

A

Stimulates the sustenacular cells

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99
Q

What is the role of inhibin hormone in spermatogenesis?

A

Secreted by sustenacular to inhibit follicle stimulating hormone

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100
Q

From where are FSH and LH spermatogenesis hormone released? Why should they sometimes be inhibited?

A

Gonadtropins secreted by the anterior pituitary; provide negative feedback

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101
Q

What do the undifferentiated gonads possess that can develop into male?

A

Wolffian ducts

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102
Q

What do the undifferentiated gonads possess that can develop into female?

A

Mullerian ducts

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103
Q

What happens to undifferentiated gonads in the absence of a Y chromosome?

A

Mullerian duct development occurs by default and female internal genitalia result

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104
Q

The external female genitalia result from mullerian duct development. T/F

A

False: not derived from the Mullerian ducts

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105
Q

What happens when the Y chromosome leads to development of male internal and external genitalia; which hormones are produced?

A

Testosterone an Mullerian inhibiting factor (MIF)

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106
Q

What produces Mulliran inhibit factor and what does it cause and prevent?

A

Testes; regression of Mullerian duct, prevents development of female internal genitalia

107
Q

When does testosterone secretion begin?

A

Around week 7 of gestation

108
Q

When are the testes formed based on gestation?

A

Week 9

109
Q

What supplies testosterone in gestation?

A

Interstitial cells

110
Q

What happens to the testosterone responsible for the development of male external genitalia?

A

Enters the systemic circulation and must be converted to dihydrotestosterone in target tissues to exert its effect

111
Q

What are the three main fetal precursors of the reproductive organs?

A

Wolffan ducts, Mullerian ducts and gonads

112
Q

What happens to the Wolffian ducts during female development?

A

They disappear in female reproductive system

113
Q

What happens for the Mullerian ducts during male development?

A

Disappear

114
Q

Why are female and male structures considered analogous?

A

Because they arise from different precursors

115
Q

What are testes and ovaries considered in relation to development and why?

A

Homologous organs because they are derived from the same undeveloped structures

116
Q

Based on the testis, what is this homologous organ in female and what is the function?

A

Ovary; gamete and hormone reproduction

117
Q

Based on the penis, what is this homologous organ in female and what is the function?

A

Clitoris; erectile tissue and sensation

118
Q

Based on the bulbourethral gland, what is this homologous organ in female and what is the function?

A

Greater vestibular glands; lubrication

119
Q

Based on the scrotum, what is this homologous organ in female and what is the function?

A

Labia majora, external skin folds

120
Q

What are androgens?

A

All hormones involved in the development and maintenance of male characteristics

121
Q

What are estrogen?

A

All hormones involved in development and maintenance of female characteristics

122
Q

What is the primary estrogen produced in ovaries?

A

Estradiol

123
Q

Elevated levels of testosterone are responsible for the development and maintenance of male……(based on puberty and adult life) ?

A

Secondary sexual characteristics

124
Q

What results from the maintenance of secondary sexual characteristics done by testosterone?

A

Pubertal growth spurt and fusion of the epiphyses

125
Q

The role of estrogen in the female is________to the role of testosterone in the male.

A

Analogous

126
Q

What is estrogen required for at the beginning of puberty for females?

A
  1. Regulate the uterine cycle

2. Development and maintenance of female secondary sexual characteristics

127
Q

What causes the fusion of epiphyses in females?

A

Estrogen

128
Q

What is sex steroid production controlled by and by which hormone?

A

The hypothalamus and the anterior pituitary; gonadotropin releasing hormone

129
Q

Where is the gonadotropin releasing hormone found?

A

In hypothalamus

130
Q

What does the gonadotropin releases hormones stimulate?

A

Stimulates the pituitary to release the gonadotropins

131
Q

What do the gonadotropins release based on pituitary stimulation?

A
  1. Follicle-stimulating hormone (FSH)

2. Luteinizing hormone (LH)

132
Q

What does the LH stimulate in men?

A

The luteinizing hormone acts in interstitial cells to stimulate testosterone production

133
Q

What does the FSH stimulate in men?

A

The follicle-stimulating hormone stimulates the sustenacular cells

134
Q

What does the LH stimulate in women?

A

The luteinizing hormone stimulates the formation of the corpus lute and progesterone secretion

135
Q

What does the FSH stimulate in women?

A

Stimulates the granulose cells to secrete estrogen

136
Q

What does feedback inhibition by the steroids based on androgens and estrogens?

A

Inhibits the production of GnRH, LH and FSH

137
Q

What cells produce inhibin based on estrogen and androgen?

A

Produced by sustenacular cells and the granulosa cells

138
Q

What type of feedback does inhibin provide?

A

Provides further feedback regulation of FSH production

139
Q

Why are the structures of female and male genitalia considered homologous?

A

Derived from a common undifferentiated precursor

140
Q

When there is the undifferentiated precursor, what does the testosterone cause to happen during male formation?

A

Causes a pair of skin folds known as labioscrotal swellings to grow and fuse, forming the scrotum

141
Q

When there is the undifferentiated precursor, the lack of testosterone causes what to happen during female formation?

A

The labioscrotal swellings form the labia majora of the vagina

142
Q

The structure that becomes the clitoris in the female is located where?

A

Located within the labia majora in the uppermost part of the vulva

143
Q

What is the name of the body part in female where the urine exists the body?

A

Urethral opening

144
Q

What surrounds the urethral opening?

A

Another pair of skin folds called the labia minora

145
Q

Why doesn’t the female internal genitalia have no homologous structures in the males?

A

Because female internal genitalia are derived from the Mullerian ducts

146
Q

What is the cervix?

A

The part of the uterus which opens into the vagina

147
Q

What is the endometrium and what is it responsible for?

A

Innermost lining of the uterus; responsible for nourishment and menstrual bleeding

148
Q

What surrounded the endometrium of the uterus?

A

Myometrium

149
Q

What is the myometrium?

A

A thick layer of smooth muscle comprising the wall of the uterus

150
Q

What does the uterus end into?

A

Two uterine tubes of finger-like structures called fimbriae

151
Q

What does the fimbriae brush ups gainst?

A

The ovary

152
Q

Is estrogen production by the ovaries required for the development of the uterine tubes and uterus?

A

No, the Mullerian ducts develop into vaagina, uterus and uterine tubes by default as long as MIF is absent

153
Q

What are the stages of the female sexual act?

A

Arousal, orgasm and resolution

154
Q

What parts in females contains the erectile tissue?

A

Clitoris and labia minora

155
Q

What is lubrication provided by in female sexual act?

A

Greater vestibular glands and vaginal epithelium

156
Q

When does oogenesis begin?

A

Prenatally

157
Q

What do germ cells do in the ovary of a female fetus?

A

Divide mitotically to produce large numbers of oogonia

158
Q

What is the difference between germ cells mitotic division in female and males?

A

Only happens in adult males

159
Q

Oogonia go through all meiosis during fetus development in females T/F

A

False: enter first phase of meiosis and arrested in orphan I - primary oocytes

160
Q

When does the number of oogonia peak?

A

Peaks at about 7 million at mid-gestation (20 weeks into the fetal life)

161
Q

What happens when the number of oogonia is peaked?

A

Mitosis ceases, conversion to primary oocytes begins and progressive loss of cells to only about 2 million primary oocytes

162
Q

How many oocytes are ever actually ovulated in the average women?

A

400

163
Q

How long can primary oocytes and female stay frozen in prophase I of meiosis?

A

For decades, until they re-enter the meiotic cycle

164
Q

What stimulates completion of the first meiotic division and ovulation in female body’s?

A

Hormonal changes

165
Q

The first meiotic division caused by hormonal changes yields what in females?

A

A large secondary oocyte and a small polar body

166
Q

What does a small polar body contain in females?

A

Half of the DNA and no cytoplasm or organelles

167
Q

When does the second meiotic division occur in females?

A

Only if the secondary oocyte if fertilized by a sperm

168
Q

What is the result of the second meiotic division in females ?

A

Large ovum and second polar body

169
Q

What must the sperm and egg what for in order to fuse?

A

Wait for the secondary oocyte to release the second polar body and finish maturing to an ootid and then an ovum

170
Q

Where is the primary oocyte found?

A

Granulosa cells, clump of sporting cells

171
Q

The oocyte and the granulosa cells are called what?

A

Follicle

172
Q

Granulosa cells assist with what?

A

Maturation

173
Q

What is the male counterpart of granulosa cells?

A

Sustenacular cells

174
Q

What is an immature primary oocyte surrounded by? What does it form?

A

Surrounded by a single layer of granulosa cells forming a primordial follicle

175
Q

What is the zona pellucida?

A

Oocyte forms a protective layer of mucopolysaccharides

176
Q

If there are several follicles in an ovary, what are they surrounded and separated by?

A

Thecal cells

177
Q

What is the male counterpart of the thecal cells? What do they respond to?

A

Testicular interstitial cells, stimulated by LH

178
Q

What happens to the several maturing follicles in the ovary?

A

One of them progresses to the point of ovulation each month and all the others degenerate

179
Q

Since one of the follicles progress, what is it called based on maturating of follicles?

A

Graafian follicle

180
Q

What happens to the Graafian follicle during ovulation?

A

Bursts, releasing the secondary oocyte with its zone pellucid and protective granolas cells into the Fallopian tube

181
Q

What is the corona radiata?

A

The layer of the granulosa cells surrounding the ovum

182
Q

What is the corpus luteum?

A

The follicular cells remaining in the ovary after ovulation form this structure

183
Q

Where is estrogen made and secreted during first half of menstrual cycle?

A

By the granulosa cells with help from the thecal cells

184
Q

What happens based on hormones during the second half of the menstrual cycle?

A

Both estrogen and progesterone are secreted by corpus luteum

185
Q

How does estrogen exert its effect on a cell?

A

Cytoplasmic receptor binds estrogen and binds to specific DNA elements in promoters and enhancers to regulate transcription

186
Q

What events does the menstrual cycle include?

A
  1. Ovarian cycle

2. Uterine cycle

187
Q

What are the three phases of the ovarian cycle?

A
  1. Follicular phase
  2. Ovulatory phase
  3. Luteal phase
188
Q

What happens during the follicular phase of the ovarian cycle?

A

A primary follicle matures and secretes estrogen

189
Q

What controls the maturation of the follicle during the follicular phase?

A

The control of follicle stimulating hormone (FSH)

190
Q

Where is the follicle stimulating hormone from?

A

From the anterior pituitary

191
Q

How long does the follicular phase lasts for?

A

About 13 days

192
Q

What happens during the ovulatory phase of the ovarian cycle?

A

A secondary oocyte is released from the ovary

193
Q

What is the ovulatory phase, the release of the secondary oocyte, triggered by?

A

A surge of luteinizing hormone (LH) from the anterior pituitary

194
Q

During the ovulatory phase, what causes does the surge cause?

A

The remnants of the follicle to become the corpus luteum

195
Q

When does ovulation typically occurs?

A

Day 14 of the cycle

196
Q

What happens during the luteal phase of the ovarian cycle?

A

Full formation of the corpus luteum in the ovary

197
Q

What does the corpus luteum secrete based on the ovarian cycle?

A

Secretes both estrogen and progesterone and has a life spa of about two weeks

198
Q

What is the average length of the luteal phase?

A

About 14 days

199
Q

What is the focus of the uterine cycle?

A

The preparation of the endometrium for potential implantation of a fertilized egg

200
Q

What are the three phases of the uterine cycle?

A
  1. Menstruation
  2. Proliferative phase
  3. Secretory phase
201
Q

What is menstruation triggered by?

A

The degeneration of the corpus luteum and subsequent drop in estrogen and progesterone levels

202
Q

After the menstruation is triggered and there’s degeneration of the corpus luteum, what happens due to the drop in hormone level?

A

Previous cycle’s endometrial lining to slog out of the uterus which produces the bleeding associated with this time period

203
Q

How long does menstruation last for?

A

Menstruations lasts about 5 days

204
Q

What happens during the proliferative phase of the uterine cycle?

A

Estrogen produced by the follicle induces the proliferation of a new endometrium

205
Q

How long does proliferation phase last for?

A

About 9 days

206
Q

What happens during the secretory phase of the uterine cycle?

A

Estrogen and progesterone produced by the corpus item further increase development of the endometrium

207
Q

What types of secretion does he secretory phase include?

A

Secretion of glycogen and lipids and other materials

208
Q

How long does secretory phase last for?

A

14 days

209
Q

What hormones regulate the secretion of estrogen and progesterone from the ovary during the menstrual cycle?

A

Anterior pituitary and hypothalamus

210
Q

What hormones regulate the vents in the uterus?

A

Estrogen and progesterone

211
Q

What hormones are LH, FSH and GnRH?

A

Luteinizing hormone, follicle-stimulating hormone and gonadotropin

212
Q

What hormone starts the menstrual cycle?

A

Gonadotropin

213
Q

What is gonadotropin released from and what does it do?

A

From the hypothalamus and stimulates the release of FSH and LH

214
Q

Where are LH and FSH released from? What do they stand for?

A

From the anterior pituitary and stand for luteinizing hormone and follicle-stimulating hormone

215
Q

What happens under the influence of FSH that was stimulated from GnRH in the hypothalamus?

A

The granulosa and thecal cells develop during the follicular phase and secrete estrogen

216
Q

What does the secretion of estrogen from the granulosa and thecal cells do?

A

Inhibits the secretion of GnRH, FSH and LH

217
Q

What happens to estrogen through the follicular stage?

A

Increases throughout the follicular stage and reaches a threshold near the end of this case - has a positive effect on LH secretion

218
Q

Near the end of the follicular stage phase, the positive effect on LH secretion from estrogen aids in what?

A

Sudden surge in LH causesovulation

219
Q

What happens to LH after ovulation?

A

Induces the follicle to become the corpus luteum and to secrete estrogen and progesterone

220
Q

The secretion of estrogen and progesterone after the follicle becomes the corpus luteum marks the beginning of what?

A

Of the secretory phase

221
Q

When pregnancy doesn’t occur, what happens to ovulation that had formed?

A

Combined levels of estrogen and progesterone feedback to strongly inhibit secretion of GnRH, FSH and LH

222
Q

What happens when LH secretion drops near the end of the secretory phase?

A

LH secretion drops, the corpus luteum regresses, no longer secretes estrogen or progesterone and menstruation occurs

223
Q

What is the physiological reason for endometrial shedding?

A

Decrease in estrogen and progesterone levels which occurs as the corpus luteum degenerates

224
Q

Why does the corpus luteum degenerate?

A

Due to a decrease in luteinizing hormone

225
Q

Why does LH hormone decrease?

A

Feedback inhibition from the high levels of estrogen and progesterone secreted by the corpus luteum

226
Q

What should be prevented during pregnancy?

A

Ovulation

227
Q

What is doe to prevent ovulation during pregnancy?

A

Constant high levels of estrogen and progesterone seen during pregnancy to inhibit secretion of LH by the pituitary

228
Q

No LH equals…..

A

No ovulation

229
Q

What happens within a few days if fertilization takes place?

A

Embryo becomes implanted in the endometrium

230
Q

When the embryo is implanted in the endometrium, what begins to develop?

A

The placenta

231
Q

What is the chorion?

A

Portion of the placenta that is derived from the zygote

232
Q

What does the chorion secrete?

A

Human chorionic gonadotropin

233
Q

What does the human chorionic gonadtropin allow during the hormonal change of pregnancy ?

A

For corpus luteum to be maintained

234
Q

What hormone is tested for pregnancy tests?

A

hGC because its presence absolutely confirm the presence of an embryo

235
Q

What is the secondary oocyte surrounded by?

A
  1. Corona radiata

2. Zona pellucida

236
Q

What is the corona radiata?

A

A protective layer of granulosa cells

237
Q

Where is the zona pellucida located?

A

Located just outside the egg cell membrane

238
Q

What is sperm capacitation?

A

Involves the dilution of inhibitory substances present in semen

239
Q

During fertilization, what fuses?

A

Spermatozoa and secondary oocyte

240
Q

What must a sperm penetrate in order to fertilize?

A

Corona radiata and zona pellucida

241
Q

What does the sperm use in order to penetrate the two layers to fertilize?

A

The acrosome reaction

242
Q

What is the acrosome of a sperm?

A

Large vesicle in the sperm head containing hydrolytic enzymes which are released by exocytosis

243
Q

What happens after the corona radiata has been penetrated, what does the acrosome of the sperm completes?

A

The acrosome process which contains actin elongates towards the zona pellucida

244
Q

What does the acrosome process contain?

A

Bindin, a species-specific protein which bins to receptors in the zona pellucida

245
Q

What happens when the acerosome of the sperm binds to the zona pellucida?

A

Sperm and egg plasma membrane fuse and the sperm nucleus enters the secondary oocyte

246
Q

What is polyspermy?

A

Penetration of an ovum by more than one per

247
Q

What is polyspermy usually prevented by?

A

Fast block to polyspermy and slow block to polyspermy

248
Q

What is fast block to polyspermy?

A

Depolarization of the egg plasma membrane

249
Q

What is the slow block to polyspermy?

A

Calcium influx caused by the initial depolarization

250
Q

What is the slow block also known as?

A

Cortical reaction

251
Q

What are the two components of the cortical reaction?

A
  1. Swelling of the space between the zona pellucida & plasma membrane
  2. Hardening of the zona pellucida
252
Q

What is the effect. of the calcium influx during the slow blow polyspermy?

A

Causes increased metabolism and protein synthesis, also known as egg activation

253
Q

What is the first stage of fertilization?

A

Cleavage

254
Q

What is the result of the first few cell divisions that occur?

A

The morula

255
Q

The morula is the same size as the zygote, dividing cells spend most of their time where?

A

In the S and M phases, skipping the G1 and G2 phases

256
Q

What stage is after the morula?

A

Blastocyst

257
Q

What is the process of creating the blastocyst?

A

Blastulation

258
Q

What does the blastocyst contain?

A

A ring of cells called the trophoblast surrounding a cavity and an inner cell mass

259
Q

Where is the inner cell mass located based on the blastocyst?

A

Inner cell mass adhering to the inside of the trophoblast at one end of the cavity

260
Q

What will the trophoblast give rise to?

A

The chorion (zygote’s contribution to the placenta)

261
Q

What does the inner cell mass of the blastocyst become?

A

Become the embryo

262
Q

If two inner cell masses form in the blastula, what will be the result?

A

Pair of identical twins sharing the same placenta

263
Q

What happens to the developing blastocyst based on its location?

A

Reaches the uterus and burrows into the endometrium

MCAT BIOLOGY FLASHCARDS (23 decks)

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