Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

CELL BIOLOGY AND PHYSIOLOGY > week 10 - testicular function > Flashcards

week 10 - testicular function Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

spermatozoa / sperm

A
  • No transcription
  • No endoplasmic reticulum
  • No cytoplasm
  • Relies on post-translational modifications.
    o Glycosylation
    o Phosphorylation
    o Disulphide cross linking, ubiquitination, acetylation and methylation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

after ejaculation

A

Sperm – egg interaction is fertilisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is spermatogensis

A

Biological process of producing mature sperm cells, and occurs in the male gonad

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

the male reproductive organs

A
  • Scrotum provides cooler environment compared to body
    o 35-36 degrees C
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Spermatogenesis
what

A
  • Start at puberty, caused by the initiation of pulsatile release of gonadotropin releasing hormone (GnRH) from the hypothalamus
  • Takes 74 days
  • Humans produce 1000 spermatozoa/heartbeat = 100-200 million/day
  • Poor quality:
    o 95% abnormally formed
    o 68% immotile
    o 42% dead

(cells are linked – cytoplasm holds them together)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

post pubertal testis

A
  • Two products
    o Spermatozoa and hormones
  • Two compartments
    within seminiferous tubules (90%)
  • Sertoli cells
    o Nurture germ cells in testis
  • Developing germ cells
    o Spermatogenesis (haploid)
    o Spermiogenesis (differentiation into sperm cell)
    Between tubules (interstitial cells 10%)
  • Leydig cells
    o Androgen (mainly testosterone) producing cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

stertoli cells

A

Critical for all aspect of spermatogenesis (nurse cells)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

stertoli cells
Tight junction with…

A

adjacent Sertoli cells
- Maintain the spermatogonial stem cell niche

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

stertoli cells
form blood testis barrier…

A

tight Junction with adjacent sterol cells
1. Separates developing germ cells from immune system
2. Controlled chemical microenvironment for spermatogenesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

stertoli cells
Form intimate…

A

associations with germ cells (50-50)
o Adheres junction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

stertoli cells
Form a syncytium-like epithelial monolayer in which…

A

germ cell embedded – gap junctions
o Exchange molecules and communication

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

stertoli cells
final process

A

o Phagocytose cytoplasm of spermatozoa
 SPERIMATION

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

stertoli cells
Secrete fluid into…

A

lumen of seminiferous tubules which flush spermatozoa into rete testis and epididymis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

stertoli cells
Secrete Inhibin and Androgen Binding Proteins to…

A

regulate and maintain spermatogenesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

spermatogenesis
process

A
  • At puberty, prospermatogonia (gonocytes) are reactivated and undergo mitosis in basal compartment of seminiferous tubule
  • Spermatogonia are a reservoir of self renewing stem cells (maintain germ cell line) and remain in the basement of the seminiferous tubule as undifferentiated spermatogonia
  • Some “type As” spermatogonia will for “type A” spermatogonia and start process of spermatogenesis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

mitotic proliferation

A
  • Each “type A” spermatogonium undergoes mitosis to form type B spermatogonia which divide again to form primary spermatocytes which will undergo meiosis
  • All primary spermatocytes are identical to spermatogonia
  • Primary spermatocytes move towards lumen and through blood testis barrier
  • Primary spermatocytes enter a resting phase where chromosomes duplicate ready for first meiotic division
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

meiotic divisions

A

Meiosis I:
- Primary spermatocytes divide to form secondary spermatocyte
Meiosis II:
- Secondary spermatocytes divide to form haploid spermatid
Giving rise to variation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

SPERMATOGENESIS
how XX or XY

A

1 primary spermatocyte (diploid) produces
–> 4 round spermatids (haploid)

so when join female
XX or XY

19
Q

SPERM DEVELOPMENT

A

Spermatogonia (base)
–> spermatocytes
–> spermatids
–> (spermiogenesis)
–> spermatozoa (released into the lumen)

Spermatocytes and spermatids move into adluminal compartment disrupting junctions between Sertoli cells

20
Q

CELL DIFFERENTIATION
- SPERMIOGENESIS / CYTODIFFERENTIATION

A
  • Round spermatids elongate to form spermatozoa
  • Sperm are highly specialsed
    o Although very simplistic
  • Formation of specialised sperm structure
    o Acrosome, centriole, flagellum, mitochondria, nucleus
21
Q

CELL DIFFERENTIATION
ACROSOME

A
  • Formed from golgi apparatus which migrates to one end of nucleus
  • Contains hydrolytic enzymes which are released upon binding to the zona pellucida of the egg
    o Aid penetration
22
Q

CELL DIFFERENTIATION
FLAGELLUM

A
  • Centrioles migrate to opposite end of nucleus to acrosome and form axoneme
  • For sperm movement through the female tract and penetration of the egg vestments
  • Sperm centrioles also important for 1st division of the zygote
23
Q

CELL DIFFERENTIATION
MITOCHONDRIA

A
  • Helically arranged around first part of flagellum (midpiece)
  • Energy for motility
24
Q

CELL DIFFERENTIATION
CYTOPLASM

A
  • Superfluous cytoplasm forms residual body (cytoplasmic droplet) which is phagocytosed. By Sertoli cells, loss of organelles such as ER
    o All our mitochondria derived from mother
  • Sperm have very little cytoplasm
25
Q

CELL DIFFERENTIATION
NUCELUS

A
  • Sex determination (X or Y)
  • Reshaping and elongation of nucleus
  • Sperm DNA becomes highly condensed
    o Histones replaced by protamines
     Protect paternal genome during transport male and female reproductive tracts
  • Transcriptionally and translationally inactive
    o Because of protamines
    During nuclear chromatin re-organisation in spermiogenesis:
  • Somatic histones are firstly replaced by testis-sepcific histone variants
  • Transition proteins are incorporation in the nuclei of spermatids
  • Protamine’s then replace transition proteins in the late spermatids to pack genome into the highly condensed sperm nucleus
    o So no transcritption factors can reach DNA
26
Q

DEVELOPING SPERM CELLS FORM A SYNCYTIUM

A
  • Share cytoplasm
  • During meiosis and mitosis cytokinesis is incomplete
    o Intercellular bridges
  • Syncytia persist until final stages of spermatogenesis
27
Q

DEVELOPING SPERM CELLS FORM A SYNCYTIUM
- FUNCTION

A
  • Allows sharing of cytoplasmic components
    o E.g. developing sperm that carry a Y chromosome, can be supplied with essential proteins encoded by genes on the X chromosome (axoneme and acrosome
28
Q

SPERMATOGENESIS
- SPERMIATION

A
  • Last step of spermatogenesis
  • Facilitated by Sertoli cell cytoskeleton
  • Cytoplasmic bridges rupture (syncytium)
  • Loss of spermatids cytoplasm
    o Absorbed by the Sertoli cell (phagocytosis)
  • Sperm are released into lumen of seminiferous tubule in testis
29
Q

spermatogenesis
process (simple)

A

Spermatogonia → Primary spermatocytes → Secondary spermatocytes → Spermatids → Sperms

30
Q

ENDOCRINE CONTROL OF SPERMATOGENESIS
Hypothalamus-Pituitary-Gonadal Axis

A
  • Controlled by products released by testis somatic cells:
    o Within tubules
     Sertoli cells
    o Between tubules
     Leydig cells
31
Q

ENDOCRINE CONTROL OF SPERMATOGENESIS
- extra testicular regulation (puberty)
HYPOTHALAMUS

A
  • Pulsative release of GnRH (gonadotropin-releasing hormone) which act on the anterior pituitary
32
Q

ENDOCRINE CONTROL OF SPERMATOGENESIS
- extra testicular regulation (puberty)
ANTERIOR PITUITARY GONADOTROPHINS

A

FSH - follicle stimulating hormone

LH - luteinizing hormone

33
Q

ENDOCRINE CONTROL OF SPERMATOGENESIS
- extra testicular regulation (puberty)
ANTERIOR PITUITARY GONADOTROPHINS
FSH

A

o Acts on testis (Sertoli cells) to maintain spermatogenesis
o Binds to FSH receptor on Sertoli cells
o Induce expression of androgen receptors on Sertoli cells, increasing their responsiveness to androgens
o Stimulates production od ABP (androgen binding protein) by Sertoli cells
o Stimulates production of inhibin by Sertoli cells

34
Q

ENDOCRINE CONTROL OF SPERMATOGENESIS
- extra testicular regulation (puberty)
ANTERIOR PITUITARY GONADOTROPHINS
LH

A

o Binds to LH receptors mainly on Leydig cells (but also on Sertoli cells)
o Induce Leydig cells to produce androgen (testosterone)

35
Q
A

androgen

inhibin

36
Q

TESTICULAR HORMONES
androgen

A

(testosterone – steroid hormone)
- Development of testis (embryo)
- Sexual function and characteristic (puberty)
- Reproductive function (adult)
- Produced by Leydig cells (between tubules)
- Mainly testosterone:
o Carried by ABP (androgen binding protein) in testicular fluid
o Converted to dihydrotestosterone (by 5alpha-reductase in Sertoli cells)
o Binds and affects Sertoli cells’ function
- Negative feedback on hypothalamus and anterior pituitary by repressing LH and FSH production

37
Q

TESTICULAR HORMONES
inhibin

A

(protein heterodimer hormone)
- Produced by Sertoli cells
- Acts on pituitary gland
- Inhibit FSH production

38
Q

ROLE OF TESTICULAR PRODUCT

A

Androgen Binding protein (ABP)
- Product of Sertoli cells under testosterone stimulation
- Binds and carries testosterone in testicular fluid of seminiferous tubules
- Maintain high levels of testosterone 100x more concentrated than blood
o Testosterone lipid soluble and diffuse across plasma membrane
o Binding to ABP prevents diffusion and increase concentration

39
Q

MOVEMENT OF SPERM IN SEMINIFEROUS TUBULES AND RETE TESTIS

A
  • Spermatozoa released from testis are immotile until they traverse epididymis
    o Acquired caput
  • No cilia
    o But fluid secretions from Sertoli cells and smooth muscle-like cells in testicular tunic and lamina propria (collagen and elastin) of seminiferous tubules
  • Periodic powerful contraction
    o Peristalsis
40
Q

SPERM MATURATION AND TRANSPORT

A
  • Human sperm are 10-15um in length
    o Have to transverse 30-40cm of male and female reproductive tract to reach the oocyte
  • ~1 in a million complete the journey
  • Post testis:
    o Sperm need to undergo sperm maturation in the male tract (epididymis) and capacitation (further changes) in the female tract
    o Important for the acquisition of motility and fertility potential
41
Q

EPIDIDYMAL MATURATION (sperm maturation)

A
  • Highly segmented organ that is divided in 3 main anatomic regions

CAPUT - close testis (motility)
CORPUS - fertilising ability
CAUDA/ VAS DEFERENS - storage
VAS DEFERENS

Each segment:
- Displays different expression of genes
- Maintains luminal ions concentrations
- Essential to regulate steps of sperm maturation

42
Q

EPIDIDYMAL MATURATION (sperm maturation)

A

Sperm changes during epididymal transit
- Sperm interact with epididymal epithetical cells (removal of cytoplasmic droplet)
o Retention of cytoplasmic droplet is associated with reduced fertility
- Change sperm proteome – protein, lipid and sugar content
o Incorporated into the sperm cells
- Change in sperm surface
o Removal and/or modification of external proteins, sugars and lipid sperm membrane
- Intracellular signalling pathways activation during transit
o Addition or removal of protein phosphate groups (phosphorylation

43
Q

EJACULATION

A
  • Sperm (2-5%) + seminal plasma = semen
  • Approx. 3ml in human (~100 million sperm)
  • Seminal plasma is secreted by the accessory sex glands
    o seminal vesicles, prostate, Bulbourethral gland
  • transport, nutrition, buffering, antioxidants
44
Q
A

CELL BIOLOGY AND PHYSIOLOGY (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions