M4 & M5: Spermatogenesis & spermiogenesis

Gametogenesis

production of gametes. Seen in both male and female

spermatogenesis

production of sperm

oogenesis

production of egg

Continuous

timeline of production of gametes in males

seminiferous tubules

where the division and maturation of sperm cells occur

polar bodies

the other products aside from polar bodies will turn smaller and degenerate after a round of meiosis

adolescence and adulthood

occurence of spermatogenesis

Before birth

occurence of oogenesis

Sprematozoa

spermatogenesis begins at puberty of an animal, by which spermatogonia are transformed into _______

Primordial germ cells

these can be recognized in the sex cords of the testis and is surrounded by supporting cells (primitive sustentacular cells)

Seminiferous tubules

after puberty, the cell cords acquire a lumen and develop into ____

Spermatogonia

after puberty, PGCs will develop into ____

sertoli cells

Ater puberty, the Primitive sustentacular cells will develop into ____

spermatocytogenesis

Meiotic phase

Spermiogenesis

subdivisions of Spermatogenesis

Spermatocytogenesis

• “proliferative phase”

• sperm stem cells (spermatogonia) increase by mitosis , forming spermatocytes

Meiotic phase

• two sets of divisions of spermatocyted into spermatids

Spermiogenesis

• “shaping phase”

• round cells of spermatids transform into flagellated and streamlined spermatozoa WITHOUT CELL DIVISION

Physical support

Paracrine regulation

Forms blood-testis barrier

Spermatogonia

• located in the peripheral areas of the seminiferous tubules

• adjacent to basal lamina

Type A1 spermatogonia

• stem cells for spermatogenesis

• undergoes mitosis to form another Type A1 spermatogonia

Type 2 spermatogonia

• has the ability to proceed through spermatogenesis

• will give rise to intermediate spermatogonia

Primary spermatocytes

• produced from mitotic division of type B spermatogonia

• cells will also start to relocate from periphery to luminal compartments of seminiferous tubules

Secondary spermatocytes

• result of completion of meiosis I

• haploid

spermatids

• divides into 2 after meiosis II

Spermatozoa

spermatids transform into WITHOUT CELL DIVISION

Golgi phase

Cap phase

Acrosomal phase

Maturation phase

4 phases of spermiogenesis

Golgi phase

• will produce acrosomal granules to form a large acrosomal granule

• the proximal centriole will be attached to the nucleus

• the distal centriome becomes the axoneme

Cap phase

• acrosomal granule flattens and will cover a larger portion of the nucleus

Acrosomal phase

• chromatin in the nucleus condenses

• acrosomal granule is restructured into acrosome that shapes the anterior part of the sperm head

Acrosome

• shapes the anterior part of the sperm head

• contains enzymes

• for penetrating the zona pellucida of egg

Manchette

• microtubule-based structure

• surrounds the posterior region of the sperm head

Basal lamina

where the spermatid rotates and the acrosome faces to

lumen

where the developing tail of spermatid faces to

Maturation phase

• structure of sperm head is developed

• organelles were separated and forms residual body

Head

Tail

Parts of spermatozoon can be seen using light microscope

neck

middle piece

principal piece

emd piece

Parts of spermatozoon can be seen under electron microscope

Head

• contains nucleus that determines the shape of head

• anterior portion is covered by acrosome

• posterior portion = postacrosomal region

• Perinuclear theca: cytoskeletal coat that surrounds the nucleus

Neck

• short

• develops from the proximal centriole

• distal centriole continues into the axoneme of the tail

• centrioles are surrounded by coarse fibers

Middle piece

• consists of axoneme

• axoneme is surrounded by coarse fibers

• the end of this portion is marked by the annulus

principal piece

• longest portion

• contains axoneme

• mitochondrial helix is no longer present

• coarse fibers fused into fibrous sheath

end piece

• seen by the absence of fibrous sheath

• axoneme still extends

• doublets are reduced into singlets