Unit Four “Male Reproductive System”

Human Reproductive System Origin The organs that allow males and females to reproduce come from one of three germ layers that differentiate soon after fertilization During the first trimester three germ layers begin to separate to form the various organs and structures of the human body The three germ layers are: –1. Endoderm –2. Mesoderm –3. Ectoderm

Human Reproductive System Origin Ectoderm gives rise to skin, nails, hair follicles, sweat glands, and nerves within the lungs –Neuroectoderm is a specialized portion of the ectoderm that gives rise to the brain, spinal cord, peripheral nerves, and muscles and bones in the face

Human Reproductive System Origin Mesoderm gives rise to the heart, kidneys, various bones and muscles, blood vessels, as well as portions of the reproductive and urinary system Endoderm gives rise to the lungs, liver, pancreas, intestines, and the lining of the respiratory and gastrointestinal tracts

Human Reproductive System Origin The previous three germ layers begin to form the organs and structures of the body fifteen days after fertilization Once a baby is born he/she has the required sex organs for reproduction

Male Reproductive System Two main categories: –1. Primary Sex Organs – Paired Testes –2. Secondary/Accessory Sex Organs – Epididymis, Vas Deferens, Ejaculatory Duct, and Urethra

Male Reproductive System Primary Sex Organs – Testes –Testes are defined as oval shaped organs suspended in the sacs of the scrotum and are the site of sperm and hormone production –Hormones are also known as Androgens –Each testis is divided into approximately 250 compartments that contain tubules where sperm is constantly produced

Male Reproductive System Male sex hormones, like Testosterone, are secreted by cells located between the Seminiferous Tubules Cells that secrete hormones are called “Endocrine Cells” Since these endocrine cells are located between the tubules, they are called “Interstitial Cells”

Male Reproductive System

Secondary/Accessory Sex Organs –Epididymis – a long narrow tube at the back of the testes that connects the testes to the vas deferens; enables movement of sperm from testes to vas deferens –Vas Deferens – additional tube through which sperm continue their journey from the epididymis to the ejaculatory duct

Male Reproductive System Secondary/Accessory Sex Organs - Ejaculatory Duct – continuation of tube from the vas deferens through the prostate into the urethra allowing for the movement of sperm toward their final destination - Urethra - canal through which urine is discharged from the bladder and through which semen is discharged in the male

Male Reproductive Anatomy

Spermatogenesis Spermatogenesis is the production of sperm via Meiosis At puberty (12 to 14 years of age), the Interstitial Cells begin producing Androgens At the same time, the Seminiferous Tubules also enlarge, and begin to produce sperm

Spermatogenesis

1. Spermatogonia – diploid germ cells 2. Spermatogonia divide via Mitosis to produce more diploid cells 3. Some Spermatogonia become Primary Spermatocytes 4. Primary Spermatocytes enter into Meiosis I 5. After Meiosis I, they are Secondary Spermatocytes 6. After Meiosis II, there are four Spermatids that differentiate into Sperm

Anatomy of Sperm Sperm also known as Spermatozoa, have three parts: –1. Head – contains nucleus (DNA) and Acrosome (possesses enzyme to penetrate egg) –2. Middle Piece – presence of Mitochondria provide energy for movement of the tail –3. Tail – used for locomotion and powered by the Mitochondria in the Middle Piece

Anatomy of Sperm

The Prostate The Prostate surrounds the Urethra adjacent to the bladder The Prostate secretes a thin, milky fluid that is alkaline/basic. This adjusts the pH of the semen. The fluid secreted by the Prostate also enhances the motility of the sperm Prostate enlargement and cancer are common problems in men 50 and older

Male External Genitals There are two external genitals: –1. Penis – the structure that releases the sperm into the female reproductive tract –2. Scrotum – the structure that contains the developing sperm

Male External Genitals The penis becomes erect in preparation for sexual intercourse as a result of a large influx of blood to the tissue within the penis Erectile Dysfunction/Impotency is the result of the tissue in the penis not expanding enough to retain the blood previously introduced into the penis

Reproductive System Overview IY8