Figure 1-4. A, Schematic section through the wall of the seminiferous tubule. Spermatogonium just under
the outer surface of the tubule wall (basal side) undergoes mitosis to produce daughter cells, which may either
continue to divide by mitosis (thus renewing the spermatogonial stem cell population) or commence meiosis as
primary spermatocytes. As spermatogenesis and spermiogenesis occur, the differentiating cell is translocated
between adjacent Sertoli cells to the tubule lumen. Daughter spermatocytes and spermatids remain linked by
cytoplasmic bridges. The entire clone of spermatogonia derived from each primordial germ cell is linked by
cytoplasmic bridges. (Larsen, 4th ed)
Figure 1-4, cont’d. B, Structure of the mature spermatozoon. The head contains the nucleus capped by
the acrosome; the midpiece contains coiled mitochondria; the tail contains propulsive microtubules. The inset
micrograph shows the head of a human sperm. C, Bull sperm labeled with fluorescent markers to reveal its
nucleus (blue) in its head, mitochondria (green) in its midpiece, and microtubules (red) in its tail. The red labeling
around the perimeter of the head is background labeling (Larsen 4th ed)
Laparoscopic observation of spontaneous human ovulation. A remarkably prominent vascular pattern was
observed on the mature follicle (F, white arrows). A small follicular area called the stigma (S) was seen
like a reddish bleb from the follicular surface, with viscous yellow fluid (black arrows) evaginating outward into
the peritoneal cavity. The viscous fluid probably carried with it the cumulus–oocyte complex, surrounded by
several thousand small granulosa cells known as corona radiata.
Lousse. Laparoscopic observation of ovulation. Fertil Steril 2008.
Received November 13, 2007; revised and accepted December 13, 2007.
Reprint requests: Jacques Donnez, M.D., Ph.D., Department of Gynecology,
Universit e Catholique de Louvain, Cliniques Universitaires St.
Figure 1-6. A, Schematic depiction of the ovary showing folliculogenesis and ovulation. Five to 12 primordial
follicles initially respond to the rising levels of
follicle-stimulating hormone (FSH) and luteinizing hormone (LH), but only one matures. In response to the
ovulatory surge in LH and FSH, the oocyte of this
mature graafian follicle resumes meiosis and ovulation occurs. Final steps of meiosis take place only if the
released oocyte is penetrated by a sperm (Larsen, 4th ed)
Figure 1-14. Fertilization. A, Spermatozoa wriggle through the cumulus mass and release their acrosomal
enzymes on contact with the zona pellucida.
Acrosomal enzymes dissolve the zona pellucida and allow sperm to reach the oocyte. Simultaneous with fusion
of the membranes of the fertilizing sperm and oocyte, cortical granules of the oocyte release their contents,
which causes the zona pellucida to become impenetrable to other sperm. Entry of the sperm nucleus into the
cytoplasm stimulates the oocyte to complete the second meiotic division (Larsen, 4th ed)
Montage transmission electron micrograph of a human sperm cell. The cell has a compact nucleus,
conspicuous mitochondria, no endoplasmic reticulum, minimal cytoplasm and a large tail (about 45 µm in
length). Superfluous cytoplasm and associated machinery is jettisoned when the sperm emerges from the testis,
leaving a ‘stripped down’, minimalist cell ( Barratt et al.: The human spermatozoon – a stripped down but refined machine, Journal of Biology 2009, 8:63)