Biolgoy Sect 1

The cell (from Latin cella, meaning "small room"[1]) is the basic structural, functional, and biological unit of all known living organisms. Cells are the smallest unit of life that can replicate independently, and are often called the "building blocks of life".

Semen is the male reproductive fluid, containing spermatozoa in suspension. Sperm is a male reproductive cell. Prostate is a gland surrounding the neck of the bladder in male mammals and releasing prostatic fluid. Urethra is a duct by which urine is convey out of the body from the bladder, and which in male vertebrates also conveys semen. Penis is the male genital organ of higher vertebrates, carrying the duct for the transfer of sperm during copulation. Glans is the head of a penis. A shaft is the cylindrical part of the penis between the scrotum and head. Seminiferous tubules is any of the numerous long convoluted tubules in the testis which are the sites where spermatozoa mature. Seminal vesicles is each of a pair of glands that open into the vas deferens near its junction with the urethra and secrete many of the components of semen. Bladder is a membranous sac in human and other animals, which urine is collected for excretion.

It connects with these glands through two distinct pathways. Neurosecretory cells in the hypothalamus produce chemicals that communicate with the anterior pituitary via the blood vessels in the infundibulum. After the inhibiting and releasing hormones travel through the primary plexus and hypophyseal portal veins, they exit the infundibulum and enter the secondary plexus, another capillary network that is instead located in the anterior pituitary. There they diffuse out into the cells and initiate the production of specific hormones – either tropins (which incite other endocrine glands to release their hormones) or not tropic. Neurosecretory cells in the hypothalamus produce chemicals that communicate with the posterior pituitary via, again, the infundibulum. The hormones travel the short distance through the axon in vesicles, to be stored in the axon terminals of the posterior pituitary. Action potential produced upon stimulation of the neurosecretory cells initiate release of the stored hormones into a capillary network

The testes are two ovular organs found in the male reproductive system. They are held in place by a spermatic cord, which is a collection of vessels, nerves and ducts that run from more than one part of the testes. The testes function to create the hormone testosterone; a primary male sex hormone which generates the production of sperm. The seminiferous tubules which are located in the testes are responsible for the production of sperm cells, and the sperm made in this process line the tubules until they reach maturity and are released into the lumen of the seminiferous tubule.

. The Sperm Cell contains a Nucleus and so does the Nerve Cell. The Nucleus helps control the movement and the cells reproduction.

As soon as sperm cells are deposited in the female reproductive tract and pass the cervical mucus, they undergo many biochemical and physiological changes, including changes in the pattern of sperm motility known as hyperactivation, and the sperm become competent to fertilize an oocyte, in a process called capacitation 21,22. The biochemical changes that occur in this process include an efflux of cholesterol from the plasma membrane leading to an increase in membrane fluidity and permeability to bicarbonate and calcium ions which results in an increase in bicarbonate (HCO3-) concentration and intracellular pH, Ca2+, and cyclic adenosine monophosphate (cAMP) levels. 4,23.

Matsumoto AM 2001 The Testis. I n: Felig P, Frohman LA eds. E ndocrinology and Metabolism. 4th ed ed. N ew York,NY: McGraw-Hill;

Testosterone signals to developing germ cells and then can be translated directly to changes in gene expression, known as the traditional pathway. Another way is testosterone can activate kinases to maintain spermatogenesis which is known as the nontraditional pathway. In the absence of testosterone, spermatogenesis does not proceed beyond the meiosis stage. The traditional testosterone signaling pathway starts off with the testosterone diffusing through the plasma membrane to bind with the androgen receptors (AR). The receptor then undergoes an alteration in conformation which activates receptor proteins in the cytosol. AR is then able to translocate to the nucleus where it binds to androgen response elements. It is after this that the androgen response elements and the receptors can alter the expression of genes to change cellular function. The non-classical kinase activation pathway is when testosterone interacts with the androgen receptor then activate Proto-oncogene tyrosine-protein kinase, Src, which is a non receptor tyrosine kinase protein (3). This activation of Src causes the activation of the EGF receptor via intracellular pathway. The EGF receptor then activated the MAP kinase cascade through Ras resulting in activation of RAF and MEK then later ERK (3). Once these are activated, they turn on the genes that control male sex characteristics These steps are critical to maintain spermatogenesis and male

Gametogenesis refers to the production of haploid sex cells within an organism. The haploid sex cells are composed of half of the genetic material of that from the germ-line of the parents. The process of gametogenesis could not take place without two specific organs, the ovary and the testis. These two organs, the gonads, are composed of germ cells where meiosis occurs. Meiosis is the method that makes the germ cells haploid. In both males and females, this phenomenon can be observed. In males, the genetic material is passed to offspring through a process known as spermatogenesis, and in females genetic material is passed to offspring through the process of oogenesis. However, these two processes, although similar in

The sperm meets the egg so they can produce a baby. The egg develops in a woman's ovary to the womb. The womb is just another word for uterus which just holds the baby until it is ready to come out. The egg and sperm are put together to achieve unassisted fertilization which is when the women is unable to get pregnant, The egg cell contains mitochondria, which supplies the energy for the baby to feed off of. The sperm must get through the thick cell membrane to get to the egg cell. Once inside the egg, a chemical reaction takes place to keep other sperms from gaining entry. Meanwhile, the successful sperm cell will lose its tail while its dna packed head will fuse with the nucleus of the egg.(eHow.com) A fertilized egg cell is known as a zygote. Fallowing fertilization, the zygote undergoes continuous cell division, which eventually produces a child' .The female reproductive system is designed to carry out several functions. It produces the female egg cells necessary for reproduction, called the ova or oocytes. The system is designed to transport the ova to the site of

The interstitial cells of Leydig are polyhedral cell, constitute the endocrine component of the testis. They synthesize and secrete testosterone. Leydig cells occur in clusters, which are variable in size and richly supplied by capillaries. Its nucleus is large and often located eccentrically

For assessment of sperm motility, sperm were recovered from the excised cauda epididymis and allowed to capacitate for 5 min in PBS media containing at 37C. Sperm were scored as motile if any movement was detected. The total number of sperm, the number of sperm that were motile, velocity of sperms, type of motility and the percentage of motile spermatozoa in each treatment group was calculated by Computer-assisted sperm analysis (CASA)(14). One drop of sperm suspension added onto the end of glass slide then smeared and subject to Eosin-nigrosin-stain procedure (purchased from Biodiagnostic, Egypt) to determine sperm

The follicle ruptures and releases the ovum as it travels through the fallopian tube it meets with the sperm, during this stage the sperm and ovum crate a zygote which will become the embryo.

1. Chapter number and name: Chapter 26: Our understanding of the tree of life continues to change based on new data

Testes are kept in the scrotum sac and are two oval shaped glands, about 8,5cm long and 2.5cm wide. A midline septum divides the scrotum into two halves and each testical is covered in two tunics; the Tunica vaginalis from the peritoneum and the Tunica albuginea which is a deeper tunic and a fibrous capsule. The septa from this layer then divides the testes into 250 – 300 wedge shaped compartments or lobules. It is in these lobules that seminiferous tubules are found, where sperm is made. Each lobule contains about 1 – 4 seminiferous tubules. The network into which seminiferous tubules empty is called the Rete testis. After which, the epididymis receives sperm from the rete testis network.