Reproduction in Humans Flashcards
Name the Main Components of the female reproductive system.
Fallopian Tube (Oviduct)
Ovary
Uterus
Endometrium
Cervix
Vagina
State the functions of the main components of the female reproductive system
Fallopian Tube (Oviduct) - Transports egg from ovary into the uterus
Ovary - Produces egg cells in follicles
Uterus - where embryo develops
Endometrium - the layer that a zygote implants into and is shed every month (menstrual cycle)
Cervix - tight muscle which protects fetus from outside world
Vagina - Leads from cervix to outside of body
Name the main components of the male reproductive system
Testes
Scrotum
Penis
Urethra
Epididymis
Prostate Gland
Seminal Vesicle
Vas Deferens
State the functions of the main components of the male reproductive system
Testes - production of sperm cells and testosterone
Scrotum -holds and maintains an optimum temperature for testes
Penis - penetrates vagina, releases sperm
Urethra - allows excretion of urine and semen from the body
Epididymis - stores sperm
Prostate Gland - secretes alkaline fluid to counteract vaginal acidity
Seminal Vesicle - secretes fluid (proteins and fructose) to nourish sperm
Vas Deferens - carries sperm from testes to urethra
How does the human body produce gammetes?
Gametogenesis
Name the two types of gametogenesis.
Spermatogenesis
Oogenesis
What is spermatogenesis and where does it occur?
Gametogenesis in males that leads to the production of spermatozoa, this occurs in the seminiferous vesicles.
Outline the stages of spermatogenesis.
Primordial germ cells -> Spermatogonia -> Primary Spermatocytes -> Secondary Spermatocytes -> spermatids -> 4 Spermatozoa
What is the Germinal Epithellium?
A surface layer of cells surrounding the ovaries in females and testicles in males that is involved in gametogenesis
How do primary spermatocytes form?
Primordial germ cells divide by mitosis forming spermatogonia. Growth period without further division forms primary spermatocytes.
How are spermatids formed?
Primary spermatocytes divide in meiosis I to form haploid secondary spermatocytes. Secondary spermatocytes divide in meiosis II
to form four haploid spermatids.
How do spermatozoa form?
Spermatids differentiate to form flagellum, acrosome and many mitochondria.
Name the three types of cells within the testes.
Spermatogonia
Sertoli cells
Interstitial cells (Cells of Leydig)
What are Leydig cells?
Cells located adjacent to the seminiferous tubules in the testes that secrete testosterone.
What are sertoli cells?
Cells located within the seminiferous tubules in the testes that provide nourishment and protection to cells produced during spermatogenesis
Describe the structure of a mature sperm cell
Acrosome contains digestive enzymes to penetrate the zona pellucida of the egg
Flagellum for propulsion
Many Mitochondria for energy
What is oogenesis? Where does it occur?
Gametogenesis in females that results in the production of secondary oocytes, it occurs in the ovaries
Outline the stages of oogenesis
Primordial germ cell -> oogonia -> primary oocyte -> Secondary oocyte and polar body ->ootid and polar bodies -> ovum
How do primary oocytes form?
Primary germaline cells in the ovaries(and oviduct) divide by mitosis, forming oogonia.
Growth period of oogonia without division forms primary oocytes. Meiosis begins but pauses at prophase I until puberty.
What happens during the first meiotic division of oogenesis?
Primary oocyte divides in meiosis I to form secondary oocyte. Polar body buds off and sticks to oocyte.
What is a polar body?
A haploid cell produced during meiosis in females that doesn’t have the ability to be fertilised
When is the second meiotic division of oogenesis completed?
Meiosis II is initiated but paused at metaphase II unless fertilisation occurs
What happens during the second meiotic division
Secondary oocyte develops into a fertilised ovum and second polar body
Describe the structure of the secondary oocyte
Corona Radiata -outside layer of follicle cells
Zona Pellucida- coating above cytoplasm that prevents polyspermy and hardens when cortical granules release chemicals
Haploid nucleus - fertilisation restores diploid chromosome number
Outline the stages in the development of a follicle
primary follicle -> secondary follicle -> Graafian follicle ->ovulation -> corpus luteum
What is a primary follicle?
An immature ovarian follicle surrounded by two layers of follicular cells
What is a secondary follicle?
A larger follicle that has developed from a primary follicle
Define Graafian follicle
A mature fluid-filled follicle in the ovary where an egg cell develops
What is a corpus luteum?
A mass of cells that forms from the Graafian follicle after ovulation. It serves as a temporary endocrine structure during pregnancy, secreting progesterone.
What is sexual intercourse?
The entry of the male reproductive organ and the deposition of sperm into the female reproductive tract.
Explain what happens during fertilisation.
- Spermatozoa move into fallopian tubes
- Acrosome binds to zona pellucida and releases hydrolase enzymes that digest the zona pellucida
- Membranes of sperm and secondary oocyte fuse, allowing sperm nucleus to enter oocyte
- Nuclei fuse, forming a diploid zygote
- Cortical reaction causes zona pellucida to harden, preventing polyspermy
Outline the stages of early embryo development
zygote -> blastocyst -> implantation
How does a blastocyst form?
Several mitotic divisions of zygote (cleavage) produce a ball of cells, the blastocyst
Define implantation
The early stage of pregnancy in which the blastocyst adheres and sinks into the endometrium
What is the placenta?
A temporary organ attached to the lining of the uterus during pregnancy
List the hormones involved in the female reproductive system
Follicle stimulating hormone (LSH)
Luteinising hormone (LH)
Oestrogen
Progesterone
Where is FSH secreted from and what is its function?
Anterior pituitary gland, binds to follicle cells which stimulates them to mature and secrete oestrogen
Where is LH secreted from and what is its function?
Anterior pituitary gland, initiates ovulation and stimulates the development of the Graafian follicle into a corpus luteum.
What is the function of oestrogen?
Inhibits the production of FSH and causes a surge in LH production.
What secretes progesterone and what is its purpose?
The corpus luteum, causes the development of the endometrium and inhibits the production of FSH and LH.
What happens if implantation doesn’t occur?
Corpus luteum degenerates due to decreasing FSH and LH levels. Progesterone levels decrease and the endometrium breaks down.
What is HCG?
Human Chorionic gonadotropin, secreted by the developing embryo that maintains the corpus luteum during early pregnancy.
Describe the role of the placenta during pregnancy?
Exchange of gases and nutrients
Barrier between foetal and maternal blood which protects foetus and parent from differing blood pressures
Secretes progesterone and oestrogen
Protects the mother’s immune system
What does progesterone do during pregnancy?
It suppresses contractions of the uterine wall.
What does oestrogen do during pregnancy?
Stimulates uterine growth and the development of the mammary glands
How do levels of hormones change prior to birth?
Oestrogen levels increase
Progesterone levels decrease
Why do progesterone levels decrease just before birth?
Allows the uterine wall to contract
Where is oxytocin secreted from and what is its role?
Posterior pituitary gland, triggers the contraction of the uterus wall as a result of positive feedback
Where is prolactin secreted from and what is it’s role?
Anterior pituitary gland, stimulates lactation during and after birth.
What is amniotic fluid and what is it’s role?
The liquid surrounding the embryo in the amniotic sac, protecting the foetus by acting as a shock absorber.
How is the placenta adapted for the exchange of substances between blood.
Counter-current blood flow
Chorionic villi provide a large surface area for the exchange of products.
Foetal capillaries lie close to the surface giving a short diffusion distance
Abundance of maternal blood vessels
What are intervillous spaces?
Spaces between the chorionic villi that contain maternal blood?
What is the role of the umbilical artery?
Carries deoxygenated blood from the foetus to the placenta.
What is the role of the umbilical vein?
Carries oxygenated blood from the placenta to the foetus.
