making egg and sperm & development and birth Flashcards
(48 cards)
1
Q
Mitosis
A
- 4 stages (+ interphase)
- somatic cells
- produces 2 diploid daughters
- gen. var. does not change
- no. of chromosomes stay the same
2
Q
Meiosis
A
- 8 stages (+ interphase)
- germ/sex cells
- produces 4 haploid daughter cells
- gen. var. increases
- no. of chromosomes is halved
3
Q
Female reproductive system
A
- Ovaries open into peritoneal cavity
- Fimbriae direct ovum in uterine tube/fallopian tube/oviduct
- Successful fertilisation normally occurs in the first third of the uterine tube
- Vagina
4
Q
Male reproductive system
A
Testis and scrotum
Epididymis
Vas deferens or ductus deferens
Urethra
5
Q
Seminal vesicles
A
- Prostaglandin, stimulate motility of sperm
- Fructose, nutrient source for the sperm
- Clotting agents (different from blood), coagulates semen after ejaculation
6
Q
Prostate gland
A
- Citric acid, used by sperm in ATP production (energy)
- Proteolytic enzymes, eventually breakdown clotting agents
7
Q
Bulbourethral (Cowper’s) glands
A
- Mucous (released pre-ejaculation), lubricate urethra and end of penis to prevent damage to sperm
- Alkaline fluid, neutralise acidity of urethra
8
Q
Vagina
A
channel connecting to the cervix
9
Q
Spermatogenesis
A
the process of sperm cell formation that occurs in the seminiferous tubules of the testes in males
10
Q
seminiferous tubules
A
coiled tubes, the walls of which contain cells that produce sperm
11
Q
Sperm. Proliferative phase:
A
- Undifferentiated germ cells (spermatogonia) undergo mitotic divisions to increase their numbers.
- As a result, some of the spermatogonia become primary spermatocytes, which enter the meiotic phase.
12
Q
Sperm. Meiotic phase:
A
- primary spermatocytes undergo two successive meiotic divisions to produce four haploid cells called spermatids.
- Each spermatid contains half the genetic material of the original primary spermatocyte.
13
Q
Spermatid differentiation
A
the process by which immature, haploid cells called spermatids transform into mature, highly specialised sperm cells during the final phase of spermatogenesis
14
Q
1.Formation of the acrosome:
A
- Acrosome: specialised organelle that covers the head of the mature sperm and contains enzymes needed for fertilisation.
- During spermatid differentiation, a vesicle derived from the Golgi apparatus fuses with the nuclear envelope to form the acrosome.
15
Q
2.Elongation and condensation of the nucleus:
A
The spermatid nucleus becomes highly condensed and elongated to form the head of the mature sperm.
16
Q
3.Formation of the flagellum:
A
- Flagellum: long, whip-like structure that propels the sperm.
- During spermatid differentiation, a centriole at the base of the cell elongates and forms the axoneme, the core of the flagellum.
17
Q
4.Shedding of excess cytoplasm:
A
- Immature spermatids contain a large amount of excess cytoplasm, which is removed during spermatid differentiation to create a streamlined shape for easier movement.
18
Q
Oogenesis
A
- process of egg cell formation in females.
- It occurs in the ovaries and begins during foetal development, but most of the process occurs after puberty and continues until menopause.
19
Q
Ovaries
A
- Suspended by ligaments
- Ovarian follicle containing - Oocyte, blood vessels, lymphatic vessels and nerves
20
Q
Oog. Proliferative Phase:
A
- Begins during foetal development when the primordial germ cells divide and differentiate into oogonia, which are the precursor cells of eggs.
- Oogonia undergo mitotic divisions to increase their numbers and form primary oocytes.
21
Q
Oog. Meiotic Phase:
A
- Paused at prophase I of meiosis until puberty.
- At puberty, a small number of primary oocytes are stimulated to resume meiosis I.
- One of these primary oocytes is released from the ovary during each menstrual cycle and begins meiosis II, which is only completed if the egg is fertilised.
- Meiosis results in the production of one mature egg and three nonfunctional polar bodies.
22
Q
Oog. Differentiation Phase:
A
- Occurs after fertilisation or after the primary oocyte has completed meiosis II to produce a mature egg.
- The egg undergoes further differentiation, during which it acquires the necessary organelles and molecular machinery to support early embryonic development.
23
Q
The hormones in males (before puberty)
A
Testosterone and Inhibin inhibit:
* GnRH (secreted by immature hypothalamus) and,
* Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH) secretion by the anterior pituitary gland
24
Q
The hormones in males (puberty)
A
- Begins 12-14yrs old
- Hypothalamus maturation reduces sensitivity to testosterone and inhibin
- GnRH secretion that increases Luteinizing hormone (LH) and follicle stimulating hormone (FSH)
- Enlargement of reproductive organs and development of secondary male characteristics
25
The hormones in females (before puberty)
* Oestrogen and progesterone (ovaries) **negative**-feedback
* **Low** **GnRH** (immature hypothalamus), low **LH** and **FSH** (anterior pituitary)
26
The hormones in females (puberty)
* Begins 11-13yrs old
* Maturation of hypothalamus: high GnRH, high LH and FSH
* **decrease negative**-feedback of oestrogen and progesterone
* oestrogen production increased by **developing follicle**
* **Enlargement of reproductive organs** and development of **secondary** female characteristics
27
Menses
(4-5 days)
**removal** of **superficial** layer of endometrium
Day 1 of cycle – first full day bleeding
28
Proliferative Stage (menstrual)
* Sustained **increase** in **oestrogen** stimulates **GnRH** secretion by hypothalamus
* **GnRH** triggers **LH** and **FSH** secretion from anterior pituitary
* **FSH** stimulates oestrogen prod. by **develop**. **follicles**, results in **positive** feedback
* Large increase in **LH** triggers **ovulation** (approx.day 14) which is the start of the secretory stage
29
Secretory Stage, Corpus luteum
* Secretes **progesterone** and small amounts of **oestrogen**
* Progesterone **thickens** endometrium and causes fluid secretion (nutrients for embryo)
* Progesterone and oestrogen inhibit hypothalamus and anterior pituitary and hence **LH** and **FSH** secretion **decline** after ovulation
30
If fertilisation...
(7-8 days after ovulation)
* **Endometrium** becomes fully **developed**
* Human chorionic gonadotropin (**HCG**) production by the trophoblasts during implantation of the embryo which **maintains corpus luteum**
31
If no fertilisation...
(menses)
* Endometrium **sloughed**
* Corpus luteum **degenerates**, reducing progesterone
* **Increase FSH**
32
Fertilisation Day 0
* Preventing **polyspermy**
Two mechanisms prevent more than one sperm:
1. **Fast block (Na+)** diffuses into **oocyte** from extracellular space, and
2. **Slow block (Ca2+)** release by ER, initiate cell division (complete **meiosis**) and trigger cortical reaction
33
Zygote
Formed when pronuclei of sperm and egg fuse
34
Cleavage Day 1 to 6
repeated **mitotic division** as the **embryo** migrates down the **oviduct** to the uterus
35
Implantation Day 7 to 10
The developing embryo **attaches** to the **lining** of the **uterus** and begins to receive **nutrients** and **oxygen** from the mother's blood supply.
36
Gastrulation Day 12
* The inner cell **mass** of the blastocyst undergoes complex cellular and molecular changes that result in the formation of the three germ layers: the **endoderm, mesoderm, and ectoderm**.
* These germ layers will give rise to all the different **tissues** and **organs** of the body.
37
Neurulation Day 18
* **Ectoderm** differentiates into the **neural plate**, which will eventually give rise to the central nervous system (**CNS**)
* **Folding** of neural tube determines position of:
**Grey** matter (unmyelinated neurons and cell bodies) and
**White** matter (myelinated neurons) in CNS
38
Organogenesis begins around 3 to 8 weeks and continues until birth
Depends on the development of different organs
Brain: week 3
Heart: week 3, the 4 chambers formed in week 7
Kidneys: week 9
* From **fertilisation to week 7** a developing human is referred to as an **embryo**.
* From **week 8 to birth**, the developing human is called a **foetus**
39
Gestation 280 Days
... 40 weeks or 9 months (3 trimesters)
40
Parturition
* **Dilation** of the **cervix** (**contractions** of the **uterine** muscles)
* Descent and expulsion of the **baby** through the **birth canal**
* Delivery of the **placenta**.
41
Developmental origins of health and disease
the exposure to **environmental** factors during **gestation** (prenatal) and the first year after birth (**perinatal**) will determine the development of human diseases in **adulthood**
42
Which of the following best describes the feedback mechanism between the gonads and the hypothalamus/pituitary gland in females?
It is sometimes **positive** feedback and sometimes **negative** feedback
43
Gonads
**glands** that produce **hormones** that are involved in **reproduction** and other functions of the body
44
chimera
a single organism composed of cells with more than one distinct genotype
45
embyonic development
1. Production of a **polar** **body** through meiosis II
2. **Mitosis**
3. Leaving the **zona pellucida**
4. **Implantation**
46
The stages of embryonic development
**Z**ygote > **M**orula > **Bl**astocyst > **G**astrula
47
The largest number of oocytes are produced in the ovaries during which period of life:
birth
48
Which is the first developmental stage when all three cell layers are present?
gastrula
