4.2 sexual reproduction in humans Flashcards
What are the male reproduction system specialized for?
- Produce, maintain and transport sperm
- Discharge sperm within female reproductive tract
- Produce and secrete male hormones (testosterone)
Define spermatogenesis.
The process of sperm production within the seminiferous tubules in the testes.
What are the female reproductive system specialized for?
- To produce female reproductive cells
- As the site of development of a foetus
- To produce and secrete female sex hormones.
What is the function of the penis?
The penis is the male organ for sexual intercourse and urination. It contains erectile tissue that fills with blood making the penis erect.
What is sperm?
Sperm need to be kept in an aquatic environment as they have to swim, so secretions are added - seminal fluid. Semen and urine leave the penis through the urethra.
What is the scrotum?
The scrotum is a loose, pouch-like sack of skin that hangs behind the penis, containing the testes. It has a protective function, including the maintenance of optimal temperatures for sperm survival and function.
What is the function of the testes?
The testes must maintain a temperature slightly cooler than normal body temperature. The testis is the location for testosterone production, and spermatogenesis takes place in the seminiferous tubules.
What is the vas deferens?
Transports mature sperm to the urethra in preparation for ejaculation.
What is the epididymis?
Located at the back of the testis and connects it to the vas deferens. Its function is to store and carry sperm.
What is the seminal vesicle?
Sac-like pouches that attach to the vas deferens near the base of the bladder. They produce molecules such as fructose that serve as energy sources for sperm and secrete an alkali fluid to neutralize the acidity of the vagina.
What is the prostate gland?
A walnut-sized structure located below the urinary bladder in front of the rectum. It contributes additional fluid to the ejaculate that serves as nourishment for sperm.
What is the uterus?
The site of implantation and development of the foetus, produces vaginal and uterine secretions, and passes the male sperm through to the Fallopian tube.
What are the ovaries?
They produce the female egg cells and secrete oestrogen and progesterone.
Describe the process of spermatogenesis.
- Takes place in the seminiferous tubules
- Germinal epithelium cells (2n) undergo mitosis to form spermatogonium (2n)
- Spermatogonium divide many times by mitosis to form primary spermatocytes
- Primary spermatocytes (2n) undergo meiosis to form secondary spermatocytes (n) which undergo meiosis 2 to form spermatid
- Spermatid undergoes maturation to form spermatozoa.
What are Sertoli cells?
Support developing spermatozoa and provide nutrients to these cells. They also provide protection from the male immune system.
Describe the process of oogenesis.
- Germinal epithelium (2n) undergoes mitosis to form oogonium (2n)
- Oogonium divides many times and enlarges to produce a large number of primary oocytes
- Primary oocytes (2n) are present at birth and development is delayed at prophase 1
- Secondary oocyte (n) meiosis 1 is completed just before ovulation and meiosis 2 is stopped at metaphase 2
- Produces second polar body and ovum (2n).
- Meiosis 2 of ovum will be completed if fertilization occurs.
What is capacitation?
Makes sperm more active and thins the membrane by covering the front of the head by removing cholesterol and glycoproteins.
Describe the acrosome reaction.
Releases hydrolase enzymes which digest zona pellucida, allowing sperm to move through zona pellucida and come in contact with the secondary oocyte to fuse with its plasma membrane.
Describe the cortical reaction.
In which cortical granules fuse with the cell membrane and modify the zona pellucida to form the fertilization membrane preventing polyspermy.
What is cleavage?
Following the formation of the zygote, the new diploid cell must undergo repeated mitotic divisions to increase the cell number - during this period, there is no growth in size. Zygote → 2 cells → 4 cells → 8 cells → 16 cells.
What is a morula?
A solid ball of cells that makes up an embryo; in humans, this stage occurs within four days of fertilization.
What is a blastocyst?
A hollow fluid-filled ball of cells is formed. The blastocyst has an outer layer of cells called trophoblasts which will differentiate into the chorion and placenta. The collection of cells on one side of the blastocyst is called the inner cell mass which will differentiate to produce the foetus.
