Lecture 4 - MA Male Reproduction Flashcards Preview

SMP - SDR > Lecture 4 - MA Male Reproduction > Flashcards

Flashcards in Lecture 4 - MA Male Reproduction Deck (147)
Loading flashcards...
1
Q

When do the testes descend into scrotum? How?

A

7-month-old fetus via the inguinal canal

3 phases:

  1. Testes attachment to the cranial suspensory ligament is severed + gubernaculum contracts (both hormone induced)
  2. Transabdominal descent brings testes down to inguinal ring located cranially to the scrotum
  3. Transinguinal descent brings testes into scrotum
2
Q

When do the testes develop embryologically? What is concurrent?

A

Around 13 weeks when kidney development begins

3
Q

What is the gubernaculum testis?

A

Connective tissue extending from testis to what will become scrotum

4
Q

Does the gubernaculum grow as the body grows? Consequence?

A

NOPE

As the fetus grows the gubernaculum holds the testis in a lower abdominal position

5
Q

What is cryptorchidism? Consequences? Treatment?

A

Undescended testis (or both)

Consequences: sterility (due to higher temperature inhibiting spermatozoa production) or cancer

Treatment: surgery = orchidopexy

6
Q

What is an inguinal hernia?

A

Hernia allowing a loop of intestine to descend into the scrotal area

7
Q

What disease manifests as referred pain to the testes? Why?

A

Kidney disease because kidney has related embryological origin

8
Q

What is the testicular capsule?

A

Connective tissue enclosing the testis

9
Q

3 layers of the testicular capsule? List from inner to outer. Which is thickest?

A
  1. Tunica vasculosa
  2. Tunica albuginea**
  3. Visceral tunica vaginalis
10
Q

What is the visceral tunica vaginalis?

A

Mesothelial cuboidal cell layer

11
Q

What does the tunica albuginea of the testes consist of?

A
  1. Collagen fibers
  2. Fibroblasts
  3. Nerve endings
  4. Smooth muscle cells
12
Q

How are testis divided?

A

Divided into ~250 lobules by septa branching from the tunica albuginea

13
Q

What is the mediastinum of the testis?

A

Thickening of the tunica albuginea along the posterior border of testis that supports the rete testis cavities

14
Q

What is the rete testis?

A

Anastomosing network of delicate tubules located in the hilum of the testicle that carries sperm from the seminiferous tubules to the efferent ducts

15
Q

Where is the interstitium of the testis? What does it contain?

A

Between the seminiferous tubules composed of clusters of:

  1. Leydig cells
  2. Lymphatics
  3. Blood vessels
  4. Nerves
  5. Components of loose connective tissue
  6. Lymphocytes
  7. Mast cells
  8. Macrophages
16
Q

Role of Leydig cells?

A

Produce testosterone

17
Q

4 roles of testosterone?

A
  1. Maintains spermatogenesis
  2. Maintains accessory glands of reproduction
  3. Maintains secondary sex characteristics
  4. Maintains libido
18
Q

What stimulates the Leydig cells to produce testosterone?

A

LH

19
Q

What do human Leydig cells contain?

A

Characteristic structures = crystals of Reinke

20
Q

How many seminiferous tubules in each testis lobule?

A

1-4

21
Q

Describe the seminiferous tubules of the testis.

A

Looped structures that join, at both ends, with the rete testis

22
Q

What is each seminiferous tubule surrounded by?

A

Tunica propria

23
Q

Describe the layers of seminiferous tubules.

A
  1. Complex stratified epithelium: germ cells and Sertoli cells
  2. Basement membrane: basal lamina + lamina reticularis
24
Q

What is the transitional zone of the seminiferous tubule? Other name? What is the next section?

A

End of seminiferous tubule devoid of germs cells (Sertoli cells only)

= terminal segment

Then, there is the tubulus rectus connecting the transitional zone to the rete testis

25
Q

What is special about the Sertoli cells of the seminiferous tubules?

A
  1. Only cells to extend from base of seminiferous tubule to the lumen
  2. Oval shaped nucleus
  3. Infolding of nuclear membrane
26
Q

Genome of Sertoli cells?

A

Diploid and non-proliferative in adult

27
Q

How can you recognize Sertoli cells?

A

Lobulated nucleus and indented nuclear membrane

28
Q

Why are Sertoli cells sustentacular?

A

They support surrounding germ cells in the seminiferous tubule epithelium by providing them with nutrients

29
Q

What stimulates the Sertoli cells to conduct their function?

A

FSH

30
Q

What is the morphological basis of the blood-testis barrier? What does this mean?

A

Tight junctions between adjacent Sertoli cells

Means that blood proteins cannot penetrate so the Sertoli cells regulate the transport of compounds from the blood to the adluminal compartment (actually add compounds of their own to it)

31
Q

What are the 2 functional compartments of the seminiferous tubule epithelium? Describe each. What are they divided by?

A
  1. Basal compartment: contains spermatogonia and early primary spermatocytes (preleptotene, leptotene)
  2. Adluminal compartments: contains later primary spermatocytes (zygotene, pachytene, diplotene), secondary spermatocytes, and differentiating spermatids

Divided by tight junctions between Sertoli cells

32
Q

What is spermatogenesis?

A

Process of spermatozoa formation from diploid spermatogonia to haploid spermatozoa

33
Q

Describe the 12 steps of spermatogenesis.

A
  1. Primitive type A spermatogonia containing 46 chromosomes (2n DNA) divide to yield type B spermatogonia
  2. The diploid (2n) type B spermatogonia divide by mitosis to yield tetraploid (4n) primary spermatocytes
  3. Preleptotene spermatocytes in prophase duplicate their DNA in preparation for the first meiotic division
  4. During meiotic prophase there is extensive rearrangement of chromatin as the cells pass through leptotene, zygotene, pachytene, and diplotene stages
  5. At the end of diplotene, the first reduction division occurs giving rise to 2 secondary spermatocytes (2n each)
  6. The secondary spermatocytes are short lived (8 hours) and rapidly undergo the second reduction division to yield 2 spermatids each containing the haploid complement of DNA (1n) of 23 single stranded chromosomes
  7. Within nascent spermatids the Golgi apparatus and the acrosomal granules migrate to one end of the nucleus where the acrosomal granules abut the nucleus forming the acrosomal cap
  8. A pair of centrioles migrates to the opposite end of the spermatid from the acrosomal cap, lying perpendicular to each other
  9. From the distal centriole microtubules form, which in turn form the axoneme of the sperm
  10. Mitochondria migrate to the base of the tail and surround it forming the mid-piece
  11. The manchette, a cylindrical band of microtubules, forms around the sperm nucleus as it elongates and condenses to form the sperm head
  12. Excess cytoplasm is shed as a residual body, which is phagocytosed by adjacent Sertoli cells
34
Q

What is spermiogenesis?

A

Process whereby newly formed round spermatids differentiate to form spermatozoa

35
Q

How does the reduction division from 2n to 1n occur during spermatogenesis?

A

Because no DNA synthesis takes place between the first and second meiotic divisions in secondary spermatocytes

36
Q

What does the acrosomal cap of a spermatid contain? Purpose?

A

Enzymes (acrosin, hyaluronidase, neuraminidase) that facilitate penetration of the zona pellucida during fertilization

37
Q

Describe microtubule arrangement of the axoneme of spermatids?

A

Characteristic 9+2 doublet of microtubules

38
Q

How long does the ENTIRE spermatogenesis take?

A

74 days

39
Q

What is Sertoli cell only syndrome?

A

Cause of infertility caused by aspermatogenesis. i.e., an absence of germ cells

40
Q

What can lead to complete LOSS of germ cells and infertility?

A

Irradiation of the testes by cancer treatment or nuclear accident

41
Q

4 parts of the spermatozoa?

A
  1. Head
  2. Mid-piece
  3. Principal piece
  4. End-piece
42
Q

Describe the head of the spermatozoa. Size?

A

5µm, composed primarily of a condensed nucleus with the acrosomal cap over the anterior 2/3 of the nucleus

The neck region contains the paired centrioles from which emerges the 9+2 doublet of microtubules

43
Q

Describe the mid-piece of the spermatozoa. Size?

A

5µm, composed of the 9+2 doublet of microtubules (the axoneme) surrounded by an outer circumferentially arranged layer of 9 course fibers

Around the course fibers is the cylindrical layer of mitochondria that supply the energy for motility

Attached to the mid-piece is a cytoplasmic droplet, a remnant of cytoplasm from spermatid condensation and differentiation

44
Q

Describe the principal piece of the spermatozoa. Size?

A

50µm, consists of the axoneme surrounded by the 9 course fibers

In place of mitochondria, a circumferentially arranged fibrous sheath + plasma membrane

Note: number of course fibers decline from 9 to 0 from the juxta-mid-piece region to the end-piece

45
Q

Describe the end-piece of the spermatozoa.

A

Axoneme surrounded by the plasma membrane

46
Q

What are the 6 stages of spermatogenesis? What do we call this?

A

In any cross-section of a seminiferous tubule certain types of germ cells will always be found in association with each other, so these cell associations or stages are classified in man as the 6 stages of spermatogenesis => cycle of seminiferous epithelium = sequential temporal succession of these associations up to the reappearance of the first stage

47
Q

Purpose of temperature in scrotum being 2 degrees lower than in abdomen?

A
  1. Increased O2 diffusion
  2. Decreased metabolic rate of sperm

=> greater concentration of sperm can be stored in the epididymis

48
Q

Relationship between kidney development and male reproductive system development?

A

There are 3 kidneys during development:

  1. Pronephros: very primitive
  2. Mesonephros: large kidney
  3. Metaphrenic kidney

Mesonephric duct and tubules are co-opted during embryological development to give rise to the excurrent duct system of the male reproductive system, which makes sense as their main function is fluid reabsorbtion to concentrate sperm (just like the kidney) => this includes: seminal vesicles, ejaculatory ducts, ductus deferens, epididymis, and efferent ducts

49
Q

Other name for mesonephros?

A

Middle kidney

50
Q

2 other names for efferent ducts of the testis?

A

Ductuli efferentes = vasa efferentia

51
Q

What do the efferent ducts of the testis give rise to?

A

Epididymis

52
Q

Embryological origin of seminiferous tubules, straight tubules, and rete testis?

A

Indifferent gonads

53
Q

Embryological origin of prostate?

A

Pelvic urethra

54
Q

What is the pampiniform plexus?

A

Plexus of testicular veins + testicular artery in the spermatic cord that serves as a countercurrent heat exchange system to cool abdominal arterial blood passing to the testis and epididymis and to heat venous blood returning from the testis and epididymis to the abdomen

55
Q

Treatment for testicular torsion?

A

Surgery

56
Q

What does the tunica vasculosa consist of?

A

Vascular layer consisting of a plexus of blood vessels, held together by delicate connective tissue

57
Q

What hormone do Sertoli cells produce? Role?

A

Inhibin => feedback to anterior pit to reduce FSH secretion

58
Q

What are typical steroid producing cells characterized by?

A
  1. Smooth ER
  2. Lipid droplets
  3. Mitochondria with tubular cristae
59
Q

What happens to spermatogenesis in the absence of testosterone?

A

Regression and seminiferous tubules and cessation of spermatogenesis

60
Q

What are the accessory glands of reproduction maintained by testosterone? What happens to them without testosterone?

A
  1. Seminal vesicles
  2. Prostate gland
  3. Bulbo-urethral glands

They would shrink

61
Q

What are male secondary sex characteristics?

A
  1. Facial hair

2. Musculature

62
Q

What is dihydrotestosterone (DHT)?

A

More potent testosterone (binds to receptors with 50 times the affinity) that can be produced within target tissues

63
Q

Can testosterone act directly on target tissues?

A

YUP

64
Q

How do testosterone and DHT exert androgenic effects on tissues?

A

Via androgen receptors

65
Q

What does androgen receptor defect lead to? Treatment?

A

Androgen insensitivity syndrome: male genotype (XY) but female phenotype, tall (because no effect of testosterone to close epiphyseal plate), gynecomastia (excess androgens converted to estrogen by adipose tissue aromatase) and infertility with undescended testes

Treatment for undescended testes: after puberty to allow for hormones to contribute to changes in puberty + can increase size of vaginal pouch so penetrative
intercourse can be enjoyed + ensure other steroid needs are not compromised

66
Q

Precursor to testosterone?

A

Cholesterol

67
Q

What are the tubulus rectus and the rete testis lined by in the testis?

A

Simple cuboidal epithelial cells with microvilli and occasional cilia/flagella

68
Q

Purpose of blood-testis barrier?

A

During meiosis some very unique proteins are being expressed on the germ cells, so if the immune system had access, this would mount an immune response - the barrier prevents this

69
Q

Other name for type A spermatogonia?

A

Stem cells

70
Q

Other name for type B spermatogonia?

A

Progenitor cells

71
Q

Which cells are the largest during spermatogenesis?

A

Primary spermatocytes because 4n

72
Q

Purpose of spermiogenesis?

A
  1. Reduced nucleus volume for greater motility and to protect genome from damage while transit to egg
  2. Rest of spermatozoa arranged to promote motility
73
Q

Other name for neck region of the spermatocyte?

A

Connecting piece

74
Q

Other name for course fibers of the spermatocyte?

A

Outer dense fibers

75
Q

What is the cycle of the seminiferous epithelium facilitated by?

A

Incomplete cytokinesis between germ cells connecting them by cytoplasmic bridges, which make them develop synchronously

76
Q

Describe the arrangement of cellular associations in seminiferous tubules in humans.

A

Helical distribution, so that a cross-section displays more than 1 cellular association

77
Q

How many efferent ducts per testis?

A

20 bundled together

78
Q

What is the main role of the efferent ducts of the testis?

A

Reabsorb 95% of the fluid leaving the testis to concentrate the sperm 20 fold

79
Q

Effect of excessive temperature of spermatogenesis?

A

Prevents it

80
Q

For what men are testicular cancers more prevalent?

A

Men under 40

81
Q

Can testicular cancers be cured? What to note?

A

Yes in 90% of cases and are almost always malignant

82
Q

How many spermatocytes produced per second?

A

2,000

83
Q

Can sperm released from the testis fertilize an ova? Explain.

A

NOPE because that ability will be acquired through the transit through the excurrent duct system via morphological, physiological, and biochemical modifications, aka sperm maturation

84
Q

Is sperm maturation intrinsic only?

A

NOPE also extrinsic via interaction with excurrent duct system (secretion/resorption)

85
Q

6 histologically distinct regions of the excurrent ducts? Which ones are intratesticular?

A
  1. Tubulus rectus*
  2. Rete testis*
  3. Ductuli efferentes (*first part is intratesticular)
  4. Ductus epididymidis
  5. Ductus deferens
  6. Ampulla
86
Q

What layer surrounds the epithelium of the rete testis?

A

Very dense layer of connective tissue with very few blood or lymphatic vessels

87
Q

Other name for intra-testicular efferent ducts?

A

Trans-capsule channels

88
Q

Describe the transition from intra to extra efferent ducts?

A

Several intratesticular efferent ducts continuous with the cavity of the rete testis pass through the tunica albuginea to become the extra-testicular efferent ducts

89
Q

How many extra-testicular efferent ducts are there per testis?

A

~10-20

90
Q

What are extra-testicular efferent ducts lined by? Describe roles.

A

Simple columnar epithelial with:

  1. Principal cells with microvilli: reabsorb fluid
  2. Ciliated cells: help move sperm through the ducts
91
Q

Where does most fluid reabsorption occur in the excurrent duct system? What facilitates this?

A

Efferent ducts

High degree of vascularization facilitates fluid reabsorption

92
Q

By what 3 mechanisms does fluid containing sperm move through the efferent ducts?

A
  1. Hydrostatic pressure generated from the testis
  2. Beating of cilia on ciliated cells
  3. Peristaltic contractions of a thin layer of periductal smooth muscle layer around the ducts
93
Q

3 parts of the epididymis? 2 names for each.

A
  1. Caput = head
  2. Corpus = body
  3. Cauda = tail
94
Q

What is the epididymis? What is it lined by?

A

Single, highly coiled duct, 7 meters long in man lined by a highly pseudostratified columnar epithelium composed of principal cells and several other cell types

95
Q

What characterizes the principal cells of the epididymis?

A

Very prominent Golgi (to glycosylate secretory proteins), numerous vesicles, mitochondria, RER, and long stereocilia

96
Q

Role of principal cells of epididymis?

A
  1. Protein secretion associated with sperm maturation

2. Resorption of fluid and compounds from the lumen of the ductus epididymidis

97
Q

How does sperm move along the epididymis? What to note?

A

Peristaltic contractions of a layer of periductal smooth muscle layer around the ducts

Note: cauda contains additional layers of periductal muscle

98
Q

In what part of the epididymis are sperm stored?

A

Cauda due to wider lumen

99
Q

What issue with the epididymis may lead to infertility?

A

Breakdown in one or more of the interactive components of sperm maturation

100
Q

Describe infection of the epididymis.

A

Common after puberty and can be cause by gonococcal or nonspecific infection usually following retrograde spreading of the infection from the urethra

101
Q

What is the vas deferens lined by? What to note?

A

Pseudostratified columnar epithelium with stereocilia with longitudinal folds protruding into the lumen + lamina propria

Note: folds increase in height and become branched toward the ampulla

102
Q

What is the vas deferens surrounded by?

A

3 layers of smooth muscle and adventitia:

  1. Inner longitudinal
  2. Middle circular
  3. Outer longitudinal
103
Q

What is the ampulla?

A

Terminal dilated region of the vas deferens

104
Q

Where is the ampulla located? What does it connect to?

A

Posterior to the bladder and joins the duct of the seminal vesicle to form the ejaculatory duct that enters the prostatic urethra

105
Q

Role of ampulla?

A

Mixes sperm from epididymis with secretions from accessory organs

106
Q

What are the seminal vesicles?

A

Paired with each a highly convoluted duct enclosed within a lamina propria with elastic fibers, smooth muscle, and loose connective tissue

107
Q

Lining of seminal vesicles?

A

Pseudostratified/simple columnar with folds to increase the surface area for secretion

108
Q

Why is the term “seminal vesicle” a misnomer?

A

They do not store sperm, they are secretory glands

109
Q

Role of seminal vesicles?

A

During ejaculation secretions within the vesicles are expelled by contraction of smooth muscle cells in the lamina propria (inner circular and outer longitudinal)

The secretion contains:

  1. Prostaglandins to increase uterine contractions and raise cAMP levels for sperm motility
  2. Vitamin C: metabolite for sperm motility
  3. Fructose: metabolite for sperm motility
110
Q

What is the prostate enclosed by?

A

Fibro-elastic capsule

111
Q

Organization of prostate?

A

3 branched glands around urethra surrounded by fibromuscular stroma to aid in discharge of fluid:

  1. Main glands
  2. Submucosal glands
  3. Mucosal glands

(from outer to inner)

112
Q

How many prostatic glands empty into the urethra?

A

30-50

113
Q

Lining of prostate?

A

Pseudostratified or simple columnar epithelium

114
Q

What % of ejaculate is made of prostatic fluid?

A

30%

115
Q

What is prostatic fluid made of?

A
  1. Proteolytic enzymes
  2. Zinc
  3. Citric acid
  4. Acid phosphatase
  5. PSA = prostate-specific antigen
116
Q

What are corpora amylacea?

A

Prostatic concretions characteristic of the prostate gland, and occur in older men that can obstruct the lumen of the ducts

117
Q

What does prostatic cancer arise from?

A

Prostatic epithelium in the peripheral zone

118
Q

What men are at a higher risk of prostate cancer?

A

Blacks

119
Q

What is BPH exactly?

A

Overgrowth of the stroma of the prostate and often with secondary reactivation of epithelial proliferation

120
Q

What are bulbo-urethral glands enclosed in?

A

Thin smooth muscular sheath with both smooth and skeletal muscles in connective tissue

121
Q

What type of gland are both the prostate and bulbo-urethral glands?

A

Tubulo-alveolar glands

122
Q

What do bulbo-urethral glands secrete? Purpose?

A

Sialoglycoprotein (mucin) that acts as a lubricant of the penile urethra prior to ejaculation:

  1. Protects lining of urethra from acrosomal proteases
  2. Protects sperm from urine remnants
123
Q

What is characteristic of the bulbo-urethral glands? Explain.

A

Skeletal muscle in the connective tissue stroma but cannot be voluntarily controlled

124
Q

Other name for corpus spongiosum?

A

Corpus cavernosa of the urethra

125
Q

What surrounds the corpus cavernosa of the penis? Purpose?

A

A dense fibroelastic connective tissue layer, the tunica albuginea which forms a septum in the midline that is incomplete in the distal region to allow equilibration of blood flow between the two corpora cavernosa

126
Q

What surrounds the corpus spongiosum of the penis? Purpose?

A

Connective tissue layer with more elastic fibers (than the layer around corpus cavernosa) to allow the urethra to remain patent during ejaculation

127
Q

What is impotence? What can cause this?

A

Inability to achieve erection

Causes:

  1. Neurological dysfunction
  2. Emotional dysfunction
  3. Congenital circulatory disorders of the penis
128
Q

Infections of the penis?

A

Venereal diseases aka STD

129
Q

What is the external meatus of the penis?

A

Urethral opening on the glans

130
Q

What is the male urethra lined by?

A
  1. Prostatic urethra: transitional epithelium

2. Membranous and penile urethra: either stratified and/or pseudostratified columnar epithelium

131
Q

Does the male urethra have glands?

A

YUP, in the submucosal connective tissue

132
Q

Where can infections of the urethra spread?

A
  1. Bladder
  2. Seminal vesicles
  3. Epididymis
133
Q

Are stereocilia true cilia?

A

NOPE, they contain actin instead of microtubules so are just really long and thin microvilli

134
Q

How many lumens in seminal vesicle?

A

ONLY ONE

135
Q

What is the veramontanum? What to note?

A

Region within prostate where urethra merges with ejaculatory duct

Note: important imaging landmark because it can expand

136
Q

What are the 4 different zones of the prostate? List them from inner to outer.

Which ones typically give rise to BPH?

A
  1. *Periurethral zone
  2. *Transitional zone
  3. *Central zone
  4. Peripheral zone
137
Q

Test for cancer and/or BPH?

A

PSA assayed in blood tests (if > 4) because it can leak out into the vasculature due to disruption of the normal architecture of the prostate

138
Q

What is a unique feature of the prostate ONLY?

A

Corpora amylacea

139
Q

What is the root of the penis?

A

Fixed end attached to body wall

140
Q

What is the body of the penis?

A

Mobile tubular portion

141
Q

What is the glans of the penis?

A

Expanded distal end around urethral orifice

142
Q

What covers the glans of the penis? Other name?

A

Foreskin = prepuce

143
Q

Purpose of penis?

A

Organ to conduct internal fertilization for greater survivability of offspring

144
Q

What is male circumcision?

A

Removal of the foreskin

145
Q

Cons of circumcision?

A
  1. Painful
  2. Causes Peyronies disease in adults (curvature of the penis)
  3. Infections and poor surgical procedure can cause disfigurement and need for remedial surgery (or even amputation)
  4. Loss of sensitivity
  5. Discoloration due to scar tissue
  6. Can be considered genital mutilation due to irreversibility
  7. No informed consent
  8. Medically unnecessary
146
Q

Can a man be fertile without seminal vesicles?

A

YUP but less fertile

147
Q

Androgen insensitivity syndrome: 2 other names?

A

Androgen resistance syndrome = testicular feminization