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MEDSCI 142 > Section 4: Reproductive System > Flashcards

Section 4: Reproductive System Flashcards

1
Q

Reproductive hormones - categories

A 
Water soluble (peptides and proteins)
Lipid soluble (steroid hormones)
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2
Q

Water soluble reproductive hormones - site of secretion

A

Gonadotrophin releasing hormone (GnRH) - hypothalamus
Follicle-stimulating hormone (FSH) - anterior pituitary
Luteinising hormone (LH) - anterior pituitary
Oxytocin - posterior pituitary

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3
Q

Lipid soluble reproductive hormones - site of secretion

A

Androgens - testes
Oestrogens - ovary
Progestagens - ovary

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4
Q

Main endocrine glands controlling reproductive processes

A

Hypothalamus
Pituitary gland
Adrenal glands
Ovary
Testes

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5
Q

Main functions of gonads

A

Produce gametes

Produce reproductive hormones

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6
Q

Regulation of gonadotrophin secretion

A

Hypothalamus —(+ve feedback, GnRH)—>
Anterior pituitary: gonadotrophs –>
FSH and LH –>
Gonads

Gonads use -ve feedback (sex hormones) on anterior pituitary and -ve feedback on hypothalamus

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7
Q

Sex steroids: Androgens - testosterone

A

Main secretory product of testis

Associated with development and maintenance of male characteristics and fertility

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8
Q

Sex steroids: Types of androgens

A

Testosterone

5-α-dihydrotestosterone

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9
Q

Sex steroids: Androgens - key properties

A

Male sex development
Spermatogenesis
Sexual behaviour
Muscle development

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10
Q

Types of oestrogens

A

Oestradiol
Oestrone
Oestriol

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11
Q

Oestrogens - main role

A

Development and maintenance of female characteristics and fertility

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12
Q

Oestrogens - main site of production

A

Granulosa cells of growing follicle

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13
Q

Oestrogens - key properties

A

Female sex development
Growth of endometrium
Regulation of menstrual cycle
Bone growth

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14
Q

Progestagens

A

Major steroidal hormone of corpus luteum and placenta
Associated with preparations for pregnancy and its maintenance - ensure to provide best environment for an embryo to implant after fertilisation
Helps maintain placenta and uterus throughout pregnancy

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15
Q

Gonads

A

Ovaries and testes

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16
Q

Is testosterone produced in females

A

Yes, but about 10x less than in males

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17
Q

Is oestrogen produced in males

A

Yes, but about 10x less than in females

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18
Q

Oestrogens - oestradiol

A

Main and most important oestrogen
Produced by granulosa cells in developing follicle
Produced from puberty to menopause

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19
Q

Oestrogens - oestrone

A

Produced throughout a women’s life and also produced by men
Always present post-menopause in women
A weak oestrogen

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20
Q

Oestrogens - oestriol

A

Produced by placenta just prior to labour

Helps with softening of cervix

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21
Q

Is progestogen produced in males

A

No

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22
Q

Sex determination

A

Commitment of the bipotential gonad to a testis or an ovary

Presence of a testis determines sexual fate of embryo, against the basic feminine trend

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23
Q

SRY gene

A

Sex-determining Region on Y chromosome
Provides pathway for testes to development
In absence of SRY, embryo develops into a female (by default)

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24
Q

Sex differentiation

A

The phenotypic development of genital structures due to action of hormones produced following gonadal development

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25
Q

How is sex determination in mammals controlled

A

Genetically controlled
Y chromosome present: male gonads develop (testes)
Y chromosome absent: female gonads develop (ovaries)

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26
Q

Sex differentiation: Internal genitalia - female and male names

A 
Female = Mullerian duct
Male = Wolffian duct
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27
Q

Primitive gonad

A

Indifferent - could become either a teste or ovary

Once decision is made, the phenotype of that organism develops around it

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28
Q

Internal genitalia: Undifferentiated stage

A

Very early on development; 5th-6th week embryo
Bi-potential gonad
Mullerian and Wolffian duct both present

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29
Q

Internal genitalia: Male differentiation

A

Mullerian duct regression under control of AMH
Testosterone secreted by testis (Leydig cells) actively maintain Wolffian ducts, which develops into the epididymis, vas deferens and seminal vesicles
Testis descends from its internal position to scrotum, usually after 7th month

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30
Q

AMH

A

Anti-mullerian hormone

Secreted by sertoli cells

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31
Q

Internal genitalia: Male differentiation - for males to be fertile…

A

The testes need to descend and appear on outside of body
Usually complete by ~7th month, but if not, then need help to get them out or will be infertile and have higher risk of testicular cancer

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32
Q

Internal genitalia: Female differentiation

A

Lags behind male organogenesis because no active hormones driving this process
Wolffian ducts begin to regress slowly from about 10 weeks
Mullerian ducts persist and develop to give rise to uterine (fallopian) tubes, uterus, cervix and upper vagina

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33
Q

Male and female external genitalia develop from..

A

A single bi-potential precursor

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34
Q

Male vs female external genitalia - hormones

A

Male external genitalia is driven by hormones, female genitalia doesn’t require active hormone intervention

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35
Q

External genitalia: Male differentiation

A

Fusion of urethral folds enclosing the urethral tube –> forms shaft of penis
Labioscrotal swelings fuse in mid-line –> forms scrotum
Genital tubercle (glans area) expands –> forms glans penis (tip)

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36
Q

External genitalia: Female differentiation

A 
Urethral folds and labioscrotal swellings remain separate --> forms labia minora and majora
Genital tubercle (glans area) forms clitoris

Has more similarity than males to what it began from

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37
Q

What hormone drives male differentiation

A

Androgens - forces changes in structures

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38
Q

External genitalia: Male differentiation - testes descend into…

A

Scrotum

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39
Q

Androgen insensitivity syndrome

A

Person is XY and has testes, but genital ducts and/or external genitals are female
Mutation in androgen receptor gene –> prevents androgen function

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40
Q

Puberty

A

The physical, emotional and sexual transition from childhood to adulthood
Transition is gradual and punctuated by well-defined events

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41
Q

Hormonal changes in puberty lead to…

A

Behavioural responses

Physical changes

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42
Q

Puberty - ‘reawakening’

A

Following activity in developing embryo to produce genitalia, reproductive system ‘goes to sleep’ during childhood
Puberty is ‘reawakening’ of reproductive endocrine systems –> full secondary sexual maturation with capacity for reproduction

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43
Q

Mechanisms keeping reproductive function on hold and those that trigger puberty

A

Largely unknown

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44
Q

Plasma levels of ____ are very low during childhood until initiation of events leading to puberty

A

Gonadotrophins

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45
Q

First endocrine sign of puberty

A

An increase in plasma LH levels, and is the result of an increase in GnRH release

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46
Q

Diurnal changes in pulsatile release of LH at puberty

A

Gonadotrophin secretion (LH and FSH) occurs in early puberty at night during sleep
In late puberty, daytime LH pulses also increase
Sex steroids rise in response to increase in plasma LH

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47
Q

Secondary sexual characteristics - timeline

A

Develop at diff chronological ages in diff individuals

Sequence in which changes occur are quite characteristic for each sex

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48
Q

Tanner stage

A

Staging criteria that allows abnormalities to be detected, and comparisons made between individuals

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49
Q

Females: Sequence of events during puberty

A
  1. Breast
  2. Pubic hair
  3. Height spurt
  4. Menarche
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50
Q

Females: Breast development

A

First sign of secondary sexual maturation at age ~10-11
Oestrogen secretion leads to appearance of breast bud, followed by formation of a breast mound
Ovulation, with subsequent progesterone secretion, leads to full breast development

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51
Q

Females: Sexual hair development

A

Usually within 6 months of appearance of breast bud at age ~10-12
Due to exposure of hair follicles to androgens
Axillary hair follows ~1 years after pubic hair

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52
Q

Growth spurt

A

Stimulated by steroid hormones (oestrogen and androgen) with epiphyseal closure (bony ends) by oestrogen
Girls age ~11-12
Boys age ~13-15

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53
Q

Females: Menarche

A

Average age 12-13 years
First ovulation doesn’t take place until 6-9 months after menarche because +ve feedback mechanisms of oestrogen haven’t developed
Regular ovulatory cycles established 1-2 years after menarche

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54
Q

What does the first menstrual bleed (menarche) show

A

Doesn’t ensure the female is fertile, just shows the reproductive system has begun

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55
Q

Females: Pubic hair development before breast development

A

If pubic hair development occurs much before breast development, might indicate an androgen disorder

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56
Q

Axillary hair

A

Armpit hair

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57
Q

Males: Sequence of events during puberty

A
  1. Testis
  2. Pubic hair
  3. Penis
  4. Height spurt
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58
Q

Males vs females: Spermatogenesis and ovulation

A

Spermatogenesis begins earlier than ovulation does in females

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59
Q

Males: Testicular and penile enlargement

A

First signs of secondary sexual development is enlargement of testicles
Leydig cells enlarge and secrete testosterone –> gives rise to increased testicular size
Elongation and enlargement of penis begins within a year of testicular enlargement

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60
Q

Males: Sexual hair growth

A

Pubic hair appears ~6 months after beginning of testicular enlargement
Axillary hair begins ~18 months later, and facial hair later

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61
Q

Males: Spermache

A

Motile sperm is seen in urine at ~13-14 years
First conscious ejaculation occurs soon after
Equivalent of female ovulation - achieves fertility

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62
Q

Body shape in boys and girls is determined by differential effects of…

A

Androgen and oestrogen

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63
Q

Timing of puberty - females

A

A critical weight must be attained before activation of hypothalamo-pituitary-gonadal axis can occur
~47kg

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64
Q

Decreasing age of puberty in females

A

Attainment of a critical weight due to improvements in nutrition, healthcare and social living conditions
Signifies sufficient storage is required to sustain pregnancy and lactation

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65
Q

Precocious puberty

A

Appearance of physical and hormonal signs of puberty before:
7 years in girls
9 years in boys

Usually due to a GnRH dependent problem, often due to hypothalamic tumour
More common in females

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66
Q

Delayed puberty

A

Lack of appearance of physical and hormonal signs of puberty
13 years in girls
14 years in boys

Occurs when gonadotrophin signals from pituitary are inadequate for sex steroid hormone secretion
More common in males

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67
Q

Menopause

A

The consequence of ovaries running out of follicles

The last episode of natural menstrual bleeding signifying the end of a female’s reproductive life

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68
Q

What age does menopause occur

A

Between 50-52 years of age

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69
Q

Stages of menopause

A

Pre-menopause - regular cycle
Menopausal transition - irregular cycle
Post-menopause - after last menstrual cycle

Perimenopause - menopausal transition + ~1 year
Ovarian senescence - when ovaries stop working (don’t stop working immediately after menopause)

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70
Q

Post-menopausal oestrogen production

A

By ~1 year after menopause, ovary has essentially ceased producing hormones (ovarian senescence)
Oestrogen production reduces to less than 1/10 of previous
Oestrogen (oestrone) arises mainly from production in stromal cells of adipose tissue

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71
Q

Perimenopausal symptoms are due to…

A

Oestrogen deprivation

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72
Q

Perimenopausal symptoms

A 
Vasomotor:
- hot flushes
- night sweats
Genitourinary symptoms:
- atrophic changes
- vaginal dryness --> often pain during intercourse
Bone metabolism:
- osteroporosis (bone disease/weakness)
Behavioural/psychological changes
- depression, tension, anxiety, mental confusion
- loss of libido
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73
Q

Treatment of perimenopausal symptoms

A

Most symptoms may be prevented or arrested by oestrogen treatment

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74
Q

How many oocytes are released in the average female

A

Few

~400

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75
Q

Mature oocyte is released every __ days

A

~28

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76
Q

Anteflexion vs retroflexion

A

Most women have an anteflexed uterus - uterus is 90 degrees to angle of vagina
~20% of women will have a retroflexed uterus, which could cause some pain during menstruation or intercourse, but usually becomes anteflexed after pregnancy

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77
Q

Vagina - structure

A

An elastic muscular 7.5-9.0 cm tube extending from the cervix to the exterior of the body

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78
Q

Vagina - main functions

A

Passageway for elimination of menstrual fluids
Receives penis during sexual intercourse and holds spermatozoa before they pass into uterus
Forms lower portion of birth canal through which the fetus passes during delivery

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79
Q

Vagina - bacteria

A

Has a very acidic environment to ensure bacteria are destroyed

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80
Q

Uterus - structure

A

Small, pear-shaped organ
Has a tapering body down the side
Has multiple muscle layers

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81
Q

Predicting fetal growth

A

Uses fundal height - top of the uterus to pubic bone

Number of cm is approx the no of weeks of gestation

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82
Q

Predicting fetal growth: Fundal height - larger than expected could mean…

A

Twins
Breech birth
Gestational diabetes

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83
Q

Uterus - main functions

A

Pathway for sperm transport
Mechanical protection, nutritional support, and waste removal for developing embryo and fetus
Ejection of fetus at time of birth
Source of menstrual flow

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84
Q

Uterus: Myometrium - function

A

Contractions in muscular wall (myometrium) of uterus are important in ejecting fetus at time of birth

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85
Q

Uterus: Endometrium can be subdivided into…

A

Inner functional zone (stratum functionalis)

Outer basilar zone (stratum basalis)

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86
Q

Uterus: Endometrium - Inner functional zone

A

Contains most uterine glands - able to provide nutrition to developing embryo
Lost through menstrual cycle - entire thickness is lost, then increased growth in response to oestradiol, and becomes secretory

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87
Q

Uterus: Endometrium - Outer basilar zone

A

Adjacent to myometrium
Attaches endometrium to myometrium
Not lost during menstruation

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88
Q

Uterine/fallopian tube - function

A

Provides a rich, nutritive environment containing lipids and glycogen, for spermatozoa, oocyte, and the developing embryo

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89
Q

Where does fertilisation typically occur

A

In the ampulla

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90
Q

Uterine/fallopian tube: Epithelium lining

A

Epithelium lining of uterine tube has both ciliated and non-ciliated secretory columnar cells

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91
Q

Uterine/fallopian tube: Mucosa

A

Surrounded by concentric layers of smooth muscle

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92
Q

Transport along the uterine tube involves…

A

A combination of both ciliary movement and peristaltic contractions

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93
Q

Ectopic pregnancy

A

When the fertilised embryo is implanted in any tissue other than the uterine wall

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94
Q

Where do most ectopic pregnancies occur

A

Uterine tube

Called tubal pregnancy

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95
Q

Ectopic pregnancy - risk factors

A

Smoking
Advanced maternal age
Prior tubal damage

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96
Q

Ovary - structure

A

Oval shaped

Often white/yellow, sometimes lumpy and flattened

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97
Q

Ovary - regions

A 
Outer ovarian cortex - contains ovarian follicles
Central ovarian medulla - consists of ovarian stroma and steroid producing cells, which eventually become thecal cells
Inner hilum (hilus) - acts as a point of entry for nerves and blood vessels
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98
Q

Primordial follicle

A

The oocyte once surrounded by follicular/granulosa cells form the primordial follicle
Appear as little nests/clumps
Single layer of flattened squamous granulosa cells
Everyday, some grow, but most die

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99
Q

Primary follicles - structure

A

Increase in size of oocyte

Immature primary follicles consist of only one layer of cuboidal granulosa cells

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100
Q

Primary follicle: Zona pellucida

A

A translucent acellular layer formed by glycoproteins secreted by the oocyte
Layer between oocyte and granulosa cells
Contain receptors - allows entry of only one sperm

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101
Q

Primary follicle: Thecal cells

A

Condensation of ovarian stromal cells (known as thecal cells) that begin to form around the follicle

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102
Q

Follicle development

A

In response to FSH, some follicles get larger, producing many layers of granulosa cells surrounding the oocyte

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103
Q

Secondary follicle

A

AKA antral follicle
As granulosa cells proliferate, they produce a viscous follicular fluid that coalesces to form a single follicular antrum - called secondary/antral follicles

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104
Q

Secondary follicle: Corona radiata

A

Where the innermost layer of granulosa cells become firmly attached to the zona pellucida

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105
Q

Secondary follicle: Cumulus oophorus

A

Mass of loosely associated granulosa cells around the corona radiata
Cloud-like structure

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106
Q

Secondary follice: Theca interna and externa

A

Theca develops to become the inner glandular, highly vascular ‘theca interna’, and the surrounding fibrous capsule, the ‘theca externa’

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107
Q

Mature follicle AKA…

A

Graffian follicle

Pre-ovulatory follicle

108
Q

Mature follicle

A

As follicular antrum grows, oocyte becomes suspended in fluid
Connected to rim of peripheral granulosa cells by a thin stalk of cells

109
Q

Ovulation - structure

A

The increasing size of follicle and its position in the cortex of the ovarian stroma causes it to bulge out from the ovarian surface

110
Q

Ovulation

A

Follicle ruptures, carrying with it the oocyte and its surrounding mass of cumulus cells
Slow and carefully managed process - 10-15 mins for an oocyte to be released
Involves enzymes

111
Q

Ovulation - the oocyte is collected by…

A

Cilia on the fimbria, which sweep the cumulus mass into the uterine tube

112
Q

Corpus luteum

A

Formed by granulosa cells
Initially was an empty follicle
If no fertilisation, it stays present for only 2 weeks, then degenerates to become the albicans, and the empty follicle is absorbed back into the ovary in a few weeks/months

113
Q

Luteinisation

A

Where the antrum breaks down, the BM between the granulosa and thecal layers break down, and blood vessels invade
Associated with an increasing secretion of progestagens

114
Q

Corpus albicans

A

The white-ish scar tissue remaining
Absorbed back into the stromal tissue of the ovary over weeks to months
If fertilisation doesn’t occur, cycle starts all over again

115
Q

Corpus luteum: If the oocyte is fertilised and begins to divide…

A

The corpus luteum persists past its normal 2 week lifespan

116
Q

Fertilisation: What is the corpus luteum ‘rescued’ by?

A

It’s rescued from degeneration by hCG

117
Q

hCG

A

Human Chorionic Gonadotropin

Produced by the chorion of the embryo about 8 days after fertilisation

118
Q

hCG in blood / urine

A

The presence of hCG in maternal blood or urine is an indicator of pregnancy and is the hormone detected by home pregnancy tests

119
Q

Ovarian cycle - phases

A 
Follicular phase (day 1 to ovulation)
Luteal phase (ovulation to menstruation)
120
Q

Uterine/menstrual cycle - phases

A

Menstruation
Proliferative
Secretory

121
Q

Variation in length of menstrual cycle

A

Length of luteal phase usually 14 days - phase with least variation
Length of follicular phase is variable, and decreases as a woman ages

122
Q

Female reproductive system - summing up

A
  1. Corpus luteum regresses, oestrogen and progesterone levels are low, increased FSH
  2. FSH stimulation leads to increased follicular growth
  3. Day 6-7, see selection of dominant follicle, with increased oestradiol
  4. Oestradiol suppress FSH and LH production in pituitary
  5. Oestrogen levels rise, by day 12, a threshold conc of oestradiol is exceed. If this is maintained for ~36 hours, there is a temporary switch from a -ve to +ve feedback
  6. Oestrogen-mediated +ve feedback triggers a rise in GnRH –> LH surge
  7. LH surge induces ovulation
  8. Corpus luteum develops, see increased progesterone
  9. Elevated progesterone levels inhibit GnRH –> decreased FSH and LH
  10. Demise of corpus luteum
123
Q

High levels of oestrogen exert a ___ feedback on the ______, thereby increasing secretion of ____

A

Positive
Hypothalamus and anterior pituitary
GnRH and LH

124
Q

Follicle development - phases

A

Primordial follicle –> primary follicle –> secondary follicle –> mature follicle –> ovulation

125
Q

Connection of reproductive organs in females

A

Ovary is loosely connected to uterine tube, which enters the uterus
At base of uterus is the cervix, which protrudes partly into the top of the vagina
Vagina is separate from rectum on one side, and urinary bladder on other side

126
Q

Which structure picks up immature ovaries produced by the oocyte

A

Fimbriae (finger-like structures) on the end of the uterine tube

127
Q

Do all sperm reach the ovaries

A

No - many get lost along the way and get stuck in crypts or in the uterus

128
Q

The embryo that is fertilised will implant into….

A

The side of the uterus (endometrium)

129
Q

Uterus: Fundus

A

Top part of uterus

130
Q

Where does the uterus end

A

In the cervix

131
Q

Cervix

A

A constriction at the bottom, between the internal os and external os

132
Q

Cervix - function

A

For most of the reproductive cycle, it’s filled with a plug of mucous so no sperm and bacteria can enter through the vagina into the uterus
For a few days prior to ovulation each month, the mucous changes to allow entry of sperm

133
Q

Pathway of oocyte release

A

Ovary –> infundibulum –> uterine tube –> if sperm around, fertilisation takes place at ampulla

134
Q

Uterine tube - fimbriae

A

Covered in cilia
Beating nearly constantly
Increases frequency of beating towards ovulation
Important for collecting oocyte once ovulated

135
Q

What type of cells does the uterine tube contain

A

Lots of secretory cells - provides nutrients required for gametes and embryos to survive

136
Q

Ovary - main functions

A

Produce oocytes and reproductive hormones

137
Q

Tumours in ovary

A

Extremely large ones tend to be benign - don’t kill, just need to be removed
Others may be lethal

138
Q

The majority of the ovary is stacked of…

A

Primordial follicles

139
Q

Secondary follicle: Granulosa cells

A

Begin to specialise

The ones immediately around the oocyte = corona radiata

140
Q

Fertilisation: Futile cycle

A

Oocyte produced
Corpus luteum produced and stays in place for 2 weeks
Progesterone is produced, but not embryo
Corpus luteum dies
Endometrial layer is lost by menstruation

141
Q

Fertilisation: Fertile cycle

A

Oocyte produced
Sperm comes along
Makes embryo
After 8 days, embryo makes hCG
Corpus luteum produced and is rescued from death and remains
Layer of endometrium stays stable (not lost by menstruation)
Embryo can implant

142
Q

Where does spermatogenesis take place

A

In the seminiferous tubule

143
Q

Seminiferous tubule - structure

A

Has a BM
Interstitial cells between seminiferous tubules
Have cells inside the tubule
- many tails of mature sperm hanging out into lumen of tubule
- morphology of cells lining the tubule change as they move into lumen of tubule - mostly pre-sperm cells

144
Q

Seminiferous tubule: Sertoli cells - structure

A

Run from BM through all the cells into the lumen
Connected to each other around perimeter of seminiferous tubule
In intimate contact with sperm and pre-sperm

145
Q

Spermatogenesis - steps

A 
Spermatogonia / stem cell (2n) -->
Primary spermatocyte (2n) -->
Secondary spermatocyte (n) -->
Spermatid (n) -->
Sperm cell / spermatozoon (n)
146
Q

Sertoli cells for sperm are a bit like..

A

Granulosa cells for female oocytes

147
Q

Where does spermatogenesis take place

A

In seminiferous tubules of testes

148
Q

When does spermatogenesis occur

A

Only occurs after puberty

Huge numbers of sperm are produced constantly by the mature male; 300-600 sperm/gram of testis tissue/sec

149
Q

Spermatogenesis - phases

A

Mitotic division
Meiotic division - sexual division
Cytodifferentiation - change from a round to elongated cell

150
Q

Spermatogenesis: Spermatogonial stem cells

A

At puberty, primary germ cells are reactivated by endocrinal activity –> spermatogonial stem cells

151
Q

Spermatogenesis: Division of spermatogonia - process

A

Divides by asymmetrical mitosis
1 daughter cell remains undifferentiated - maintains stem cell pop
Other daughter cell continues to divide by mitosis, forming spermatogonia, which continue to divide by mitosis

152
Q

Spermatogenesis: Division of spermatogonia - place

A

Occurs in basal compartment of seminiferous tubules

153
Q

Spermatogenesis: When mitotic divisions of spermatogonia occurs…

A

They move between adjacent sertoli to adluminal compartment of seminiferous tubules –> they are then called primary spermatocytes

154
Q

Spermatogenesis: Division of primary spermatocytes

A

Meiosis I
DNA content doubles
Primary spermatocytes divide to produce secondary spermatocytes

155
Q

Spermatogenesis: Where do spermatogonia sit

A

On BM

156
Q

Spermatogenesis: Sertoli cells - function

A

Divide basal compartment from other two compartments of seminiferous tubules

157
Q

Spermatogenesis: Where does each type of division occur

A 
Spermatogonia = mitotic division
Spermatocyte = meiosis
Spermatids = cytodifferentiation
158
Q

Spermatogenesis: Division of secondary spermatocytes

A

Divide rapidly via meiosis II - gives 4 spermatids each with 23 chromosomes

159
Q

Spermatogenesis: Number of chromosomes in primary and secondary spermatocytes

A

Primary starts with 46

Secondary have 23

160
Q

Spermatogenesis: Spermiogenesis - takes place when

A

Takes place with round spermatids still in close proximity and attachment to Sertoli cells

161
Q

Cytodifferentiation AKA

A

Spermiogenesis

162
Q

Spermatogenesis: Spermiogenesis

A

Final process in spermatogenesis

Round spermatids differentiate the shape and become spermatozoa / sperm –> moves into lumen of seminiferous tubules

163
Q

Main function of sperm

A

To swim through female reproductive tract - has a number of diff adaptations to facilitate this

164
Q

Spermatogenesis: Spermiogenesis - structure

A

Round spermatids form a tail, a mid-piece, and a head
Mid-piece packed with mitochondria to produce energy
Head contains DNA and is covered by the acrosome

165
Q

Spermatogenesis: Spermiogenesis - Acrosome

A

A compartment filled with enzymes that are required for egg penetration
Has receptors that binds to shell of oocyte, and enzymes digest the shell so sperm can penetrate and get through to the oocyte

166
Q

Spermatogenesis: Spermiogenesis - cytoplasm

A

Excess cytoplasm of spermatid is lost into the residual body that is phagocytosed by Sertoli cells after the sperm leaves

167
Q

Spermatogenesis: Spermiogenesis - hydrodynamically adapted

A

Sheds all things unnecessary for swimming and fertilisation of egg, e.g. ER, Golgi, excess cytoplasm

168
Q

Hormonal control of spermatogenesis: LH

A

A protein hormone
Secreted from gonadotrophs and go to testes, where LH interacts with Leydig cells –> produces testosterone –> dihydrotestosterone (DHT) –> secondary sexual characteristics

169
Q

Male: Where do Leydig cells sit

A

In interstitial space between seminiferous tubules

170
Q

Males: Hormonal control of spermatogenesis: FSH

A

Travels freely in blood down to testes, then binds to receptors on Sertoli cells, which start producing androgen binding protein (ABP)

171
Q

Hormonal control of spermatogenesis: Androgen binding protein (ABP)

A

Since testosterone is a lipid hormone, it doesn’t mix with water/blood
ABP makes it soluble by binding to it –> allows testosterone and other androgens to be transported around the body
A small amount is secreted into seminiferous tubules –> testosterone can freely move across cell membrane –> support production of sperm

172
Q

Spermatogenesis: Spermatogonia in final stages

A

Spermatogonia can’t progress through final stages, so a lack of testosterone causes infertility in males

173
Q

Hormonal control of spermatogenesis: Testosterone and DHT - other effects

A

Aggressiveness, libido etc.
Too much is bad, so there is a control/endocrine system
- -ve feedback; testosterone feeds back to hypothalamus –> down-regulation of GnRH
- also feedback by testosterone at level of anterior pituitary; down-regulates production of FSH and LH

174
Q

Hormonal control of spermatogenesis: Inhibin

A

A protein activated by binding of FSH to Sertoli cells

Goes back to anterior pituitary to regulate production of FSH (not LH)

175
Q

Hormonal control of spermatogenesis: Kisspeptin

A

A hormone that binds to GnRH receptors in hypothalamus and stimulates production of GnRH

176
Q

Common features of infertile men

A

Reduced sperm count

< 20 million / mL

177
Q

Causes of male infertility

A

Oligospermia - some but limited sperm
Azoospermia - no sperm
Immotile sperm - can’t swim

178
Q

Treatments for male infertility

A

IVF - in vitra fertilisation

ICSI - IntraCytoplasmic sperm injection

179
Q

Treatments for male infertility: IVF

A

Oocytes are harvested, put in IVF droplets, and fertilised ex vivo
Requires approx 50,000 motile sperm
Helps treat men who are oligospermic

180
Q

Treatments for male infertility: ICSI

A

Suck out sperm from testes using a micropipette
A single sperm is injected directly into oocyte
Sperm doesn’t need to be motile
Can use sperm collected by biopsy from testes
Treats men who are completely infertile

181
Q

Orchidectomy

A

Removal of a testis

182
Q

Cryptorchidism

A

If testes don’t descend

Cryptorchid individuals are infertile

183
Q

Pathway of sperm

A 
Produced in seminiferous tubules -->
rete testis -->
epididymis -->
(ampulla) vas deferens -->
urethra
184
Q

How many seminiferous tubules in each testes

A

~80

185
Q

Rete testis

A

An assembly of seminiferous tubules that come together and start to form into a single tube (epididymal tubule), which enters the epididymis
From here on, there’s only one tube carrying sperm away to the vas deferens

186
Q

How long do sperm spend in the epididymis

A

10 days to 2 weeks transitioning along the epididymis

187
Q

What abilities to sperm acquire in the epididymis

A

Ability to be motile
Ability to fertilise
Reabsorb liquid from around the sperm making it more concentrated (~100 fold)

Acquiring these abilities takes 10-14 days

188
Q

How long can sperm be stored in the vas deferens

A

Several months - evolutionary advantage

189
Q

Do sperm have ability to swim in the seminiferous tubule

A

No - only gain ability to swim in epididymis

190
Q

Where is the major site of sperm storage

A

Vas deferens

191
Q

Ejaculatory duct - pathway

A

Starts at end of vas deferens, then runs through prostate gland –> prostatic urethra –> penis –> exterior of male body

192
Q

Vas deferens - length

A

~45cm

193
Q

Where does the vas deferens run

A

From the epididymis up and around the bladder

Then back down to join the ejaculatory duct

194
Q

Where do the seminal vesicles empty into

A

The ejaculatory duct, which joins the urethra at the prostate

195
Q

Males: Urethra - length

A

~20cm long

196
Q

Males: Urethra - pathway

A

Runs from bladder through the prostate to the end of the penis

197
Q

Seminal vesicles

A

Secretory glands (not storage areas) that secrete a mucoid substance containing:

  • alkaline
  • fructose
  • prostaglandins
  • clotting proteins
198
Q

Seminal vesicles - prostaglandin

A

Signalling molecule

May induce contractions in female reproductive tract

199
Q

Seminal vesicles - clotting proteins

A

Once ejaculation takes place in female reproductive tract, the semen forms a coagulum, which sticks the sperm into the female reproductive tract

200
Q

What is the last component that is ejaculated in males

A

The contents of the seminal vesicles

201
Q

Prostate - structure

A

A donut-shaped organ about the size of a golf ball

202
Q

Prostate - prosthetic fluid

A

The urethra passes through the prostate which secretes prostatic fluid into the urethra ahead of sperm during ejacuation

203
Q

What does the prostate secrete

A 
Slightly acidic (pH 6.5)
Contains citrate (for ATP)
Milky colour
Phosphate and calcium
PSA and other enzymes
204
Q

PSA

A

Prostate specific antigen

Breaks down post-ejaculation coagulum ~10-15 mins after its formed –> allows sperm to swim

205
Q

How is the acidity of prostatic fluid neutralised in semen

A

By seminal vesicle fluid (alkaline)

206
Q

Order of ejaculate

A
  1. Prostatic fluid
  2. Sperm
  3. Seminal vesicle fluid
207
Q

Males: What would happen if coagulum remains in place

A

Sperm wouldn’t be able to swim out of it and into the cervix / uterus

208
Q

What is semen

A

The combined components of ejaculate

i.e. mixture of sperm and seminal fluid

209
Q

What is semen made up of (%)

A

Sperm 10%
Seminal vesicle fluid 60%
Prostatic fluid 30%
Other secretions - small amounts

210
Q

Semen pH

A

~7.5
Prostatic fluid and seminal fluid neutralise each other
Buffered to allow it to survive long enough in the female reproductive tract

211
Q

Why does semen have a large volume of seminal vesicle fluid

A

Helps wash sperm down the reproductive tract

212
Q

Males: Benign prostatic hyperplasia (BPH)

A

Excess growth of the prostate / prostatic tissue –> occludes urethra
Causes difficulty in voiding bladder
Eventually causes weakening of bladder
Can cause urinary infections and kidneys problems

213
Q

Where does the prostatic urethra run through

A

The centre of the prostate

214
Q

Pathway of urine and BPH

A

To urinate, urine must pass through the prostatic urethra to reach the urine urethra
So, when the prostate grows excessively and expands out against its capsule, any additional growth has to be inwards –> starts to occlude urethra –> difficulty urinating

215
Q

Incidence of men requiring treatment for BPH

A

<40 is very rare
Starts increasing with increasing age
90% men over 85 years will need treatment

216
Q

Benign prostatic hyperplasia (BPH): Treatments

A

Selective 5-α-reductase inhibitor(s)
- finasteride
- dutasteride (stops prostate enlarging or shrinks it, must be on drugs for a long time)
Surgery - transurethral section of prostate
Others - prostatic urethral lift

217
Q

Function of 5-α-reductase

A

Converts testosterone to dihydrotestosterone

218
Q

Potency of dihydrotestosterone

A

2x more potent than testosterone

219
Q

__% of cancer cases in men are prostate

A

29%

220
Q

Detection vs deaths of prostate cancer

A

Detection of prostate cancer increased dramatically (PSA testing) but deaths increased less dramatically

221
Q

Prostate cancer: Autopsy cancer

A

30% of men > 50 y/o have prostate cancer at autopsy
But only 9.5% have been diagnosed with prostate cancer
i.e. 2/3 of men with prostate cancer don’t know they have it (isn’t causing any problems)

222
Q

Detecting prostate cancer

A

Men can be screened for elevated levels of PSA

May allow early detection, but also ‘over-diagnosis’

223
Q

What to do if someone has prostate cancer

A 
Watchful waiting - do nothing, but monitor the tumour
Androgen depletion
- 5-α-reductase inhibitors
- castration
- inhibitors of androgen synthesis
Inhibition of testosterone action - block androgen receptor
Surgery - prostatectomy
Others
224
Q

Prostate cancer: Prostectomy

A

Removal of prostate gland by surgery

225
Q

Proportion of men with +ve tests for PSA vs those with cancer

A

Of those who test positive, a large proportion of them will have a false +ve test result (i.e. no cancer)

226
Q

Penis - major structures

A

Corpora cavernosa (x2) - main erectile tissue
Corpus spongiosum - surrounds penile urethra and prevents occlusion during erection
Penile urethra - conducts semen and urine

227
Q

Penis - erection

A

Occurs following sexual stimulation
Release of NO and prostaglandin –> corpora cavernosa relaxes
Blood fills cavernous spaces of corpora cavernosa
Engorgement of corpora reduces venous outflow adding to the engorgement

228
Q

Erect vs flaccid penis - blood

A

Erect penis contains ~8x the blood volume of the flaccid penis

229
Q

Why does the corpora cavernosa relax when penis is erect

A

Causes walls to relax –> easier for blood to flow in

balloon analogy - stretch before blowing

230
Q

Erect penis: Why is it important for the corpus spongiosum to also fill with blood

A

Important in maintaining openness of penile urethra during ejaculation

231
Q

Viagra - sildenafil

A

Relaxation of smooth muscle in corpora cavernosa requires guanosine monophosphate (cGMP)
Enzymes phosphodiesterase breaks down GMP
Viagra inhibits phosphodiesterase (type 5) –> increased GMP –> relaxation of arteries supplying corpora cavernosa –> erection

232
Q

Urethral folds

A

Develop from mesoderm in cloacal region

233
Q

Urethral groove

A

An indentation between the urethral folds

The opening into the urogenital sinus

234
Q

Genital tubercle

A

A rounded elevation just anterior to the urethral folds

235
Q

Labioscrotal swelling

A

Consists of paired, elevated structures lateral to the urethral folds

236
Q

Male: Scrotum

A

The supporting structure for testes

Consists of loose skin and underlying subcutaneous layer that hangs from the root of the penis

237
Q

Male: Scrotal septum

A

Divides the scrotum into 2 sacs, each containing a single testes

238
Q

The seminiferous tubules contain these two types of cells

A

Spermatogenic cells

Sertoli cells

239
Q

Males: Interstitial cells AKA

A

Leydig cells

240
Q

Most sperm do not survive more than __ hours in the female reproductive tract

A

48

241
Q

Site of sperm maturation

A

Epididymis

242
Q

Males: Vas deferens AKA

A

Ductus deferens

243
Q

Males: Spermatic cord

A

Supporting structure
Ascends out of scrotum
Consists of vas deferens

244
Q

Varicocele

A

A swelling in the scrotum due to a dilation of the veins that drain the testes
Usually more apparent when person is standing and typically doesn’t require treatment

245
Q

Males: Bulbourethral/cowper’s glands - structure

A

Located inferior to prostate on either side of membranous urethra
Ducts open into spongy urethra

246
Q

Males: Bulbourethral/cowper’s glands - function

A

During sexual arousal, they secrete an alkaline fluid into the urethra that protects the passing sperm by neutralising acids from urine in the urethra
Secrete mucous that lubricates the end of the penis and lining of urethra –> decreases no of sperm damaged during ejaculation

247
Q

Ejaculation

A

The powerful release of semen from the urethra to the exterior
A sympathetic reflex coordinated by the lumbar portion of the spinal cord

248
Q

Emission

A

The discharge of a small volume of semen before ejaculation

249
Q

What do Sertoli cells produce

A

Androgen-binding protein (ABP)

250
Q

During the menstrual cycle, what is progesterone produced by

A

Corpus luteum

251
Q

What do interstitial cells (of Leydig) secrete

A

Testosterone

252
Q

During the menstrual cycle, when is the endometrium at its thickest

A

Late in the post-ovulatory phase

253
Q

During the menstrual cycle, when are LH levels at its highest

A

Just prior to ovulation

254
Q

What are the interstitial cells of the testes an important target for

A

LH

255
Q

Main function of progesterone during menstrual cycle

A

Thicken and maintain thickness of endometrium

256
Q

In the male, LH causes…

A

Testosterone production

257
Q

What is testosterone produced by

A

Interstitial (Leydig) cells

258
Q

If fertilisation does not occur, the corpus luteum..

A

Degenerates into the corpus albicans

259
Q

When does oogenesis begin in females

A

Before birth

260
Q

What does the acrosome of a sperm cell contain

A

Hyaluronidase for egg penetration

261
Q

What is repair of the endometrium during the preovulatory phase of menstruation due to

A

Rising levels of oestrogen

262
Q

During the menstrual cycle, when is progesterone at its highest levels

A

Late in postovulatory phase

263
Q

Which branch of the ANS is initiation and maintenance of an erection mained by

A

Parasympathetic

264
Q

Theca interna contains…

A

Secretory cells

265
Q

What happens just prior to ovulation

A

Oestrogen-mediated positive feedback triggers a rise in GnRH –> LH surge

MEDSCI 142 (9 decks)

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