Embryology week 14 Flashcards
What is the 2 periods human development is divided into
- Prenatal (before birth)
-Postnatal(after birth)
The development of a human from fertilization of an oocyte to birth is divided into what types of periods
- Embryonic and fatal
Explain the embryonic period:
-When it occurs
-And what it contains
- During week 3 -8
-Contains rapid visible development
Explain what happens in the fetal period
-Differentiation,Organ growth, and accelerated body growth
What does stage 1 of embryonic development begin as
- Fertilization
When does embryonic development end
- At stage 23 , which is day 56
When does critical development occur
- During the first trimester(13 weeks)
What does the Prenatal period incude
Embryonic period
Fetal period
What does the postnatal period contain
- Infancy, Childhood, Puberty and adulthood
Explain infancy and what happens during infancy
- Body grows rapidly, weight triples, 6-8 teeth emerge by age 1
What is an infant age 1 month or younger
neonate
Explain when Childhood occurs
- What it contains
- Between infancy and puberty
-Activebone ossification , apperance of primary teeth - Growth slows
When does puberty begin for males and females
- Around age 8 for females and age 9 males
What does puberty mark
- Functional reproductive capability
In adulthood when is full growth and maturity achieved
Ages 18-21
What is the definition of gametogenesis
- It is the formation and development of specialised reproductive cells (gametes)
from biopotential precursor cells
Name the types of gametogenesis and what it is
- Spermatogenesis( male gamete formation)
-Oogenesis(female gamete formation)
What is the definition of Meiosis
-Cell division involving 2 meiotic divisions
What is the purpose of meiosis
Converts diploid germ cells into haploid gametes
Explain what happens in the first meiotic division to the :
1.Chromosomes
2.Homologous chromosomes in prophase and anaphase
3.What It results in
1.The chromosome number is reduced from from (diploid )46 to 23 (haploid)
2. Homologous chromosomes pair in prophase and seperate in anaphase
2. Haploid cells
What does the second meiotic division occur without
DNA replication
What happens in second Meiotic division
Double -Chromatid chromosome divide into single-chromatid chromosomes
What does the Second Meiotic division start with
Haploid cells
What is the purpose of spermatogenesis
- Transformation of spermatogonia into mature sperm
When does spermatogenesis begin and occur
- At puberty
- Occurs in the seminiferous tubules of the testes
Explain the stages of spermatogenesis
- Spermatogonia undergo mitotic divison
-Primary spermatocytes undergo first meiotic divison, producing secondary spermatocytes - Secondary spermatocytes undergo second meiotic divison , forming 4 haploid spermatids
What is spermiogenesis
-How long does it take
When spermatids mature into functional sperm and takes 2 months
What is the role of sertoli cells
They support nurture and regulate spermatogenesis
Where is sperm stored,matured and gains motility
- In the epididymis
What does the sperm head contain
- Nucleus and acrosomes (enzymes for digestion)
What is the function of the tail of the sperm
-Enables movement , powered by mitochondria
What is Oogenesis
- Where oogonia transforms into mature ooctyes
When does oogonia become occytes
Before birth
When does oogenesis end/ continue to
- Until menopause
Explain what happens in Prenatal maturation of Oocytes:
starting with
-Oogonia
-Oogonia proliferates(increase in number) via mitosis during early fetal life
-They then enlarge and become primary occytes,surrounded by follicular cells, forming Primordial follicles
How are primordial follicles formed during prenatal maturation of occytes
- When the primary oocytes are surrounded by follicular cells, forming primordial follicles
When does postnatal maturation of Oocytes occur
- At puberty
Explain what happens in postnatal maturation after primary oocyte completes their first meiotic division
- Produce:
- Secondary oocyte
-First polar body
Explain what happens to secondary oocyte after formation in the postnatal maturation of oocytes
- Starts the second meiotic division but stops at metaphase
- It is fertilized by sperm and completes meiois to produce:
- Fertilized oocyte
-Second polar body
Describe the structure of the uterus
- Thick-walled, pear shaped muscular organ
Name the parts of the uterus
- Body
-Cervix
What does the body of the uterus contain
- Fundus and the isthmus
What does the cervix part of the uterus contain
- Internal os(opening)
-External os(opening)
Where do the uterine tubes extened from
Uterine horns to the peritoneal cavity
Name the 4 parts the Uterine tubes are divided into
- Infundibulum
-Ampulla
-Isthmus
-Uterine part
What is the function of uterine tubes
- Transport Oocytes from ovaries
-Carry sperm to fertilization sites
Explain the structure of Ovaries
- Almond-shaped reproductive glands
What is the function of the ovaries
- Produce oocytes
-Secret oestrogen and progesterone
Explain how Oocytes are transported starting with secondary oocytes
- The secondary oocyte is expelled from the ovarian follicle
-The fimbriae sweeps the oocyte into the infundibulum
-Then the oocyte travels to the ampulla via the peristalis
Explain how sperm is transported
- From the epididymis to the urethra by peristalis
Where is sperm deposited?
where do they pass through
Near the external os
Pass through the cervical canal using tail movements
What happens to the sperm that dont reach the fertilisation site
- Absorbed or degenerated
When can freshly ejaculated sperm fertilize an oocyte
- They must undergo capcitation
How long does capacitation take
7 hrs
What happens in capacitation
- It removes the glyvoprotein coat
-Increases sperm activity
-Alters the membrane components
Where does capacitation take place
- Uterus/uterine tubes
When does the acrosome reaction take place in relation to sperm maturation
After capacitation
What happens in the acrosome reaction
-What does it require
-Sperm binds to ZP3 glycoprotein on the zona pellucida
- Calcium ions,prostaglandins and progesterone
What is the function of Hyaluronidas and acrosin enzymes during sperm maturation
- Helps the sperm to penetrate the egg
What is capacitation and acrosome reaction regulated by
Tyrosine kinase
Name and Explain the first step of fertilisation with enzymes included
Passage of the sperm through the Cornoa Radiata
- Hyaluronidase enzymes ( from sperm acrosome) helps to disperse follicular cells
-
Name and explain the second step of Fertilization
- Penetration of the Zona pellucida
- Acrosomal enzymes break down the zona pellucida, allowing sper, entry
Explain the 3rd step of fertilization after sperm has entered the zona pellucida
- After sperm enters the zona pellucida, the zona pellucida undegoes changes to become impermeable to other sperms
-Lysosomal enzymes from cortical granules modify the zona and oocyte membrane
Explain the 4 step of fertilization (fusion)
- The head and tail of the sperm enter the oocyte, while the sperms plasma membrane and mitochondria remain outside
Expain what happens after the fusion of the Oocyte and sperm membrane ( Completion of Oocytes second meiosis division)
The oocyte completes meiosis 2, forming the female pro nucleus and second polar body
When and how is the male pronucles formed during fertilization
- After the oocyte completes meiosis 2
- When the sperm nucleus enlarges, forming the male pronucls
During fertilization what does the fusion of the male and female pro nuclei form
- Diploid zygote (46 chromosomes)
What is cleavage of zygote
It is a series of mitotic divisions that increase the number of cells - blastomeres without increasing the overall size
When does Clevage of zygote begin
30 hours after fertilization
When does clevage of zygote occcur
When the zygote moves through the uterine tubes toward the uterus
Name the 2 stages in the clevage of a zygote
- Compaction
- Morula Stage
Explain what happens in the compaction stage in cleavge of zygotes
+ what it is mediated by
-Blastomeres chnage shape and tighlty align into a compact ball
- Mediated by cell surface adhesion glycoproteins
What is the compaction stage necessary for forming
- The embryoblast of the blastocyst
What is morula in the cleavge of a zygote
- Developing human
When does a morula form in the Cleavage of a zygote and how many days after fertilization does it form
- when there are 12-32 blastomeres
- 3 days after fertilization
In morula stage of clevage of zygotes what does the internal cells and outer cells become
internal cells: embryoblasts
outer cells: trophoblast
Explain the first step of Blastocyst formation
+ What day does this occur
-The morula enters the uterus, and a blastocystic cavity forms.
-Fluid passes through the zona pellucida, separating blastomeres into:
Trophoblast:
Embryoblast
- 4 days after fertilization
What happens in the second step of blastocyst development on day 6
- The embryoblasts projects into the blastocystic cavity
- The trophoblast forms the blastocyst wall
- The zone pellucida degenerates
Explain the 3 step of blastocyst formation dat 6-7
- The blastocyst attches to the endometrial epithelium
- The trophoblast proliferates and differntiates into
- Cytotrophoblast
-Syncytiotophoblasts
What happens by the end of the 1 week during blastocyst formatioj
- The blastocyst
is implanted in the compact layer
