1_SPERMATOGENESIS/SPERMIOGENESIS

Anton van Leeuwenhoek (1632 – 1723)

• was a Dutch scientist who developed the early compound microscope.

• In 1677 on examination of his own ejaculate under the microscope,

• he identified tiny “animalcules” he found wriggling inside.

• He submitted this new observation to the Royal with the following caveat: “If your Lordship should consider that these observations may disgust or scandalize the learned, I earnestly beg your Lordship to regard them as private and to publish or destroy them as your Lordship sees fit.” Royal Society London 1677.

WBC, RBC, Yeast cell, Sperm cell, Bacterial cell

Microscopic Observations by Anton Van Leeuwenhoek:

Spermatogenesis

• is a sequential event by which the male undifferentiated germ cells, the spermatogonia, are transformed into mature gametes called the spermatozoa

• occurs in the seminiferous tubule

spermatozoa

Spermatogenesis is a sequential event by which the male undifferentiated germ cells, the spermatogonia, are transformed into mature gametes called the ____

spermatogonia

Spermatogenesis is a sequential event by which the male undifferentiated germ cells, the ____ , are transformed into mature gametes called the spermatozoa

original primordial germ cells genital ridge

That were implanted in the embryonic Spermatogonia are all derived from the _____

testes

The production of viable male germ cells is initiated in the male gonads, the ___

Spermiogenesis

• refers to the maturation process that transforms or metamorphoses the spermatids, the male germ cells that have completed their miotic divisions, into spermatozoa.

• During this process, essential parts of the cells are transformed such as the cytoplasm, nucleus, golgi apparatus, mitochondria and centrioles.

• process by which a spermatid matures into a spermatozoon

• occurs in epididymis

cytoplasm, nucleus, golgi apparatus, mitochondria and centrioles

During Spermiogenesis, essential parts of the cells are transformed such as the ____

Tunica vaginalis

This is a serous membrane that is present in a mammals that partially covers the testis and is formed during the descent of the testis from the peritoneal cavity to the scrotum.

Tunica albuginea

• This is a thick white fibrous capsule which encloses each testis.

• It further enters into the testis resulting to the formation of partitions or septate.

• The latter radiate through their interior, dividing them into cone-shaped lobules.

• Serves as protection

• Structural support

• Pressure control

• Organizes the internal partitions

Tubuli contorti or convoluted seminiferous tubules

• These are thickwalled tubules within the lobules that contain developing sperm cells.

• This is continuous with straight seminiferous tubules or tubuli recti.

• The tubulus rectus from each lobule unite to form a plexus called the rete testis.

• A series of sperm ducts called efferent ductules drain the rete testis and pierce the tunica albuginea to enter the head of the epididymis.

rete testis

The tubulus rectus from each lobule unite to form a plexus called the___

efferent ductules

A series of sperm ducts called ____ drain the rete testis and pierce the tunica albuginea to enter the head of the epididymis.

Tubulus rectus or straight seminiferous tubules

• This lies at the posterior border of the testis and contains the ductus epididymis wherein sperm cells undergo maturation

• Tubuli contorti or convoluted seminiferous tubules is continuous with___

Epididymis

• This lies at the posterior border of the testis and contains the ductus epididymis wherein sperm cells undergo maturation

• Site for sperm maturation/spermiogenesis

• Storage of sperm until ejaculation

• Transports sperm from the testis to the vas deferens

Vas deferens

• It is a continuation of the epididymis and lies posterior to testis and medial to epididymis.

• It is involved in transporting spermatozoa from the epididymis to the ejaculatory ducts.

Basement membrane

• This is a thin fibrous layer encapsulating the seminiferous tubules.

• Within this, structure are fibroblasts with elongated flattened nuclei widely spaced apart.

• The outside of the membrane also contains fibroblasts.

Spermatogonia

• These are group of small cells arranged in a single layer at the periphery of the seminiferous tubules.

• The cells, which lie against the basement membrane, are distinguishable because they possess darkly stained oval nuclei.

• are classified as types A and B.

Primary spermatocytes

• These cells are daughter cells of spermatogonia which have entered the growth phase of development.

• They are located immediately next to the spermatogonia.

• They are the largest cells in the seminiferous tubules.

• They are characterized by larger and darker nuclei as compared to the spermatogonia.

Synapsed chromosomes

appear as dark chromatin structures in their nucleus.

Secondary spermatocytes

• These cells result from the first maturation (equatorial) or reductional (meiotic) division of the primary spermatocytes.

• They are distinguished by their smaller size and location, as they are concentrated towards the lumen of the seminiferous tubules.

• The chromatin of these cells is larger than that of the primary spermatocyctes and more prominent than that of the spermatids.

Spermatids

• These cells are embedded in the cytoplasm of the sertoli cells.

• They emerge as small cells with short tails.

• These cells are soon to metamorphose into mature sperm cells during spermiogenesis.

Spermatozoa

• These are the mature sperm cells.

• They are distinguishable because of their relatively long tail attached to the sperm head.

Sertoli (sustentacular) cells

• These are columnar cells that are elongated and tall.

• They are located within the seminiferous tubules, interspersed between the spermatogonia.

• The ____ are identified by having a large pale nucleus and numerous spermatids embedded in the supranuclear cytoplasm.

Formation of acrosomal cap

4 major cellular organizations which result to morphological changes during spermiogenesis of all vertebrates:

• The development of the acrosomal cap is due to the coalescence of the vesicles of the golgi apparatus which pinch off from it and forms a membranous structure called the acrosome. This structure forms a cap over the nucleus initiating the rotation of the nucleus so that the acrosome points to the sheath of the seminiferous tubule.

• Formation of acrosomal cap

• Condensation of the nucleus.

• Outgrowth of the flagellum

• Sheath arrangement of the mitochondria

There are four (4) major cellular organizations which result to morphological changes during spermiogenesis of all vertebrates.

Condensation of the nucleus

4 major cellular organizations which result to morphological changes during spermiogenesis of all vertebrates:

• The loss of fluid in the nucleus makes it condense, thus, reducing its size and decreasing the concentration of its chromatin. The chromosomal histones are also replaced with proteins called protamines.\

• The nucleus becomes smaller, denser and takes on a characteristic, flattened form

Outgrowth of the flagellum

4 major cellular organizations which result to morphological changes during spermiogenesis of all vertebrates:

• At the opposite pole of the spermatid, a pair of centriole becomes the root of the growth of a group of microtubules. The posterior centriole which moves away from the anterior one forms the shape of a ring surrounding the flagellum. This organelle supports the developing flagellum which extends into the lumen of the tubule.

Sheath arrangement of the mitochondria

4 major cellular organizations which result to morphological changes during spermiogenesis of all vertebrates:

• The cell’s mitochondria aggregate around the base of the flagellum forming a spiral configuration.

Masson trichome

What stain is used to highlight connective tissue components

greening-blue hue

Using Masson trichome, what color does connective tissue septa and the interstitial tissue in amongst the seminiferous tubules appear?

Reddish color

Using Masson trichome, what color does seminiferous tubules appear?

Gametogenesis

• The formation of male and female sec cells from germ cells

testes and epididymis

are paired structures , located within the scrotum

within the scrotum

The testes and epididymis are paired structures, located ____

sperm production and hormone synthesis

The testes are the site of

storage of sperm

The epididymis has a role in the ___

posterolateral of testicle

Anatomical position of epididymis

spermatic cord

The testes is suspended from the abdomen by the ____

ellipsoid

The testes have an ___ shape

Interstitial (Leydig) cells

• where testosterone is synthesized-are present in the interstitium

• Produce and secrete testosterone

• Produce small amounts of other androgens (e.g., androstenedione), which can be converted to testosterone

interstitium

Leydig cells where testosterone is synthesized-are present in the ____

Seminiferous tubule

• site of maturation involving meiosis and spermiogenesis

• Produces sperm

• Nurtures the germ cells until maturation

• Transport system for tubular fluid towards the epididymis

• Blood-testis barrier to avoid germ cell reproduction in the immune system

• site of spermatogenesis

Spermatogonia → Primary spermatocytes → Secondary spermatocytes → Spermatids

SPERMATOGENESIS

acrosome

The ___ lies over the tip

Nucleus and acrosome

__ form the sperm cell’s head that is bound to the midpiece by a short neck

Acrosome formation

The golgi complex engender the vesicles, which then merge into a larger formation that settles colse tot he cell nucleus and finally inverts itself like a cap over the largest part of the nucleus

lysosomal enzymes (hyaluronidase among others)

The acrosome corresponds functionally to a lysosome & thus contains ___

9 peripheral double microtubules

The development of the flagellum consists of a bundle of ___ and 2 single ones in the center

The future axonemal structure grows out of one centriole (distal)

The development of the flagellum consists of a bundle of 9 peripheral double microtubules and 2 single ones in the center

Neck

4 parts of the finished flagellum can be distinguished:

• contains the two centrioles (proximal and distal)

Midpiece

4 parts of the finished flagellum can be distinguished:

• consists of a sheath of ring-shaped mitochondria grouped around the axoneme to provide the energy for the flagellar movement

Principal piece

4 parts of the finished flagellum can be distinguished:

• has a sheath of ring fibers around the axoneme

Endpiece

4 parts of the finished flagellum can be distinguished:

• consists of only the 9+2 structure of the axoneme

plasma membrane

The sperm cell is completely enveloped by the ___

Sertoli's cells

The cytoplasm of the spermatids that is no longer needed is phagocytized by ____ or is disposed of in the lumen of the tubules.

psychological factors

During sperm cell production considerable individual variations exist that are also partially influenced by ____

100 million

Per day roughly ___ sperm cells are produced.

50-200 million

It is said that in each ejaculate an average number of ____sperm cells are present (WHO standard value: over 40 million).

Interstitial connective tissue

• Provides structural support between seminiferous tubules

• Contains blood vessels, lymphatics, and nerves to nourish the testis

• Houses leydig (interstitial) cells

Oval, Smooth, Has a defined acrosome

Human sperm head

Ovoid, flattened, Has a distinct and defined acrosomal cap.

Bull sperm head

Hook-shaped/falciform, Curved with a pointed tip (helps in movement and fertilization)

Rat sperm head

Filiform (elongated and slender), Almost needle-like

Rooster sperm head