Exam 3: Spermatogenesis Flashcards
What is spermatogenesis
Production of sperm from the primordial germ cells
Formation of the sex cords
PGCs arrive at the genital ridge of male embryo, they
become incorporated into the sex cords, remain until puberty
Formation of seminiferous tubules
At puberty, sex cords hollow out to form
the seminiferous tubules
Formation of sertoli cells
Epithelium of the seminiferous tubules differentiates into sertoli cells
Purpose of sertoli cells
Surround spermatogenic germ cells to nourish and protect developing sperm
Leydig cells
Pivotal components of the testis and male reproductive system
Rete testes
Steps of spermatogensis
Proliferation: Spermatogonia A (4 forms) > Spermatogonia I > Spermatogonia B
Meiosis: Primary spermatocytes > secondary spermatocytes
Differentiation secondary spermatocytes > spermatids
After reaching the gonad, the ___ divide to form __________. These cells are _____ than the PGCs and are characterized by an ovoid nucleus that contains ______ associated with the _______ membrane.
PGCs
A1 spermatogonia
smaller
chromatin
nuclear
Fate of spermatids
Become sperm during spermiogenesis
Fate of A4 spermatogonium
self renewal, apoptosis, or differentiate into first committed stem cell type, intermediate spermatogonium
Intermediate spermatogonia
committed to becoming spermatozoa
divide mitotically once to form the type B spermatogonia. These cells
are the precursors of the spermatocytes and are the last cells of the line
that undergo mitosis. They divide once to generate the primary
spermatocytes
Fate of primary spermatocytes
Enter meiosis
Syncytium
Connection between sperm stem cells where cells communicate with each other through cytoplasmic bridges
Each _______ undergoes the first _______ to yield a pair of secondary spermatocytes, which complete the second division of meiosis. This forms the ______ cells called spermatids.
primary spermatocyte
meiotic division
haploid
During the divisions from type A1 spermatogonium to spermatid, the cells move
farther and farther away from the basement membrane of the seminiferous
tubule and closer to its lumen.
* Thus, each type of cell can be found in a particular layer of the tubule. The
spermatids are located at the border of the lumen, and here they lose their
cytoplasmic connections and differentiate into sperm cells
Purpose of spermiogenesis
Prepare the sperm to reach and bind the egg
First step of spermiogenesis
Development of acrosomal vesicle from golgi apparatus
Acrosome forms cap that covers sperm nucleus
Nucleus rotates so cap is facing seminferous tubules basal membranes
Allows flagellum emerging from centriole to extend into lumen
Last stage of spermiogenesis
Nucleus flattens and condenses, remaining cytoplasm releases, mitochondria form a ring around flagellum
Golgi phase of spermatid differentiation
A: spermatid is perfectly soherical and has well devleoped golgi apparatus
B:
C:
Cap phase
Replacement of histones by protamines (histones organize chromatins), makes sperm transcriptionally silent (protamines stack chromatin very densely)
A: golgi migrate
B:
Acrosomal phase
A: spermatid nucleus elongates, acrosome covers
B:
Maturation phase
Mitochondria form a spiral assembly around flagellem that defines middle piece
Postnuclear cap is formed
