Midterm 2 - Lecture 17 Flashcards
What are the 5 components of the semen manufacturing complex?
- Manufacturing Center = testes
- Finishing stop = forward excurrent ducts
- Warehouse Shipping = hind excurrent ducts
- Final Alteration and Shipping = accessory sex glands
- Delivery System = penis
What are the 4 goals of spermatogenesis?
- provide a male with continual supply of gametes
- provide billions of sperm each day to maximize reproductive efficiency
- provide genetic diversity
- provide an immunologically privileged site where spermatogenic cells will not be destroyed by the male’s immune system
Are males continually fertile? How?
Yes! Spermatogenesis provides the male with a continual supply of gametes
What is spermatogenesis?
sperm production
What are the 3 phases are spermatogenesis?
- proliferation
- meiosis
- differentiation (spermogenesis)
What happens during the proliferation phase of spermatogenesis?
- mitotic division (maintains diploid) of spermatogonia to form primary spermatocytes
- constant replacement of spermatogonia
What happens during the meiosis phase of spermatogenesis?
- Diploid (2N) primary spermatocytes go through meiotic division to produce Haploid (1N) spermatids
- Genetic diversity is guaranteed by processes such as homologous recombination and DNA methylation
What happens during the differentiation phase of spermatogenesis?
- spermatids develop into fully formed spermatozoa
What membrane is proliferation happening the closest to?
Basement membrane of the seminiferous tubule
What is the blood-testis barrier?
- cellular barrier that prevents immune system from affecting the developing sperm
What are the 2 cellular layers of the blood-testis barrier?
- Peritubular cells - surrounding the seminiferous tubules
- Junctional complexes - tight connections btw the sertoli cells within the seminiferous tubules
What are the 2 distinct compartments that the junction complexes divide the seminiferous lumen into?
- basal compartment - spermatogonia
- adluminal compartment - spermatocytes, spermatids, spermatozoa
Duration of spermatogenesis
- relatively long process
- spermatogonia to spermatid (~10 days)
- spermatid to spermatozoa (~50 days)
Spermatozoa
- sperm are simple cells the basic elements necessary to get DNA from the male tract into the female tract
What are 6 key features of spermatozoa?
- nucleus + genetic material
- little cytoplasm
- no endoplasmic reticulum
- numerous mitochondria (for energy)
- a tail
- plasma membrane + acrosome (w/ enzymes to penetrate oocyte)
During differentiation, to form functional sperm, spermatids must go through what 4 phases of changes?
- Golgi Phase = acrosomic vesicle formation and centriole migration
- Cap Phase = acrosomic vesicle spreads over nucleus and initiation of axoneme (tail) formation
- Acrosomal Phase = nuclear + cytoplasmic elongation & neck + annulus formation
- Maturation Phase = final assembly of sperm
What happens during the Golgi Phase of differentiation?
- golgi apparatus starts to transform into the acrosome and centrioles position to become a tail:
1.
a) small vesicles of the golgi fuse and start to produce Proacrosomic granules
b) Centrioles migrate around the Nucleus to a position opposite to the fusing Golgi
2.
a) fusion of golgi vesicles continues, to produce a large Acrosomic Vesicle containing a dense Acrosomic granule
b) Proximal Centrioles positioned to become point of attachment btw the sperm head and tail; Distal Centrioles positioned to become Axoneme (tail)
Axoneme
tail
What happens during the Cap Phase of differentiation?
- remained of the Golgi migrates around the nucleus toward the centrioles
- distal centriole starts to form the Axoneme (tail)
- acrosomal vesicle flattens and begins to form the outer acrosomal membrane, inner acrosomal membrane, and acrosomal contents (enzymes)
What happens during the acrosomal phase of differentiation?
- nucleus elongates and Acrosome stretches to cover most of the developing sperm head
- in order to give the Mitochondria access to the developing tail, Manchette microtubles form at the base of the developing sperm head and stretches the plasma membrane down
- the sperm Neck & Annulus form
What happens during the Maturation Phase of differentiation?
- Mitochondria form a spiral assembly around the tail (flagellum) to create a well defined middle piece
- Manchette tubules regress and form the Postnuclear Cap
- Cytoplasm sloughs off and forms the Cytoplasmic droplet
- Annulus forms a defined jxn btw the middle piece and principal piece
Plasma membrane of spermatid
Plasma membrane of spermatozoa
Golgi of spermatid
Acrosome of spermatozoa
Centrioles (proximal and distal) of spermatid
sperm neck and tail (flagella) of spermatozoa
Mitochondria of spermatid
Mitochondrial Sheath of spermatozoa
Cytoplasm of spermatid
Lost as a Cytoplasmic droplet of spermatozoa
Manchette of spermatid
Postnuclear Cap of spermatozoa
“the bigger the factory, the greater the output”
Testicular size is a good estimator of sperm producing ability
3 fxns of the epididymus
- Sperm concentration
- fluids that suspended the sperm in the seminiferous tubules are absorbed by the epididymal head & upper body - Sperm maturation
- as sperm move through the body of the epididymus into the upper tail they mature, become motile, and gain the potential to fertilize - Storage
- sperm are stored in the distal tail of the epididymus until the time of ejaculation
Where are sperm stored?
- in the distal tail of the epididymus until the time of ejaculation
What is the state of the sperm in the epididymal head (caput)?
- sperm is not motile & non-fertile
- cytoplasmic droplet is proximal
- testicular secretions are absorbed
What is the state of the sperm in the epididymal body (corpus)?
- sperm capable of normal motility and fertility potential
- cytoplasmic droplet begins to translocate
- sperm capable of binding to oocyte
