[4] PRELIMS | PROCESS OF CONCEPTION AND EARLY FETAL DEVELOPMENT Flashcards
Mitosis results in the production of ___ or ___, which are exact copies of the original cells
diploid body; somatic cells
In mature individuals, this is the process by which our body cells continue to divide and replace themselves
mitosis
Meiosis is a process of cell division leading to the development of ___ and ___ needed to produce a new organism
eggs and sperm
The gametes must have a haploid number (___) of chromosomes so that when the female gamete (___) and the male gamete (___) unite to form the ___ or a fertilized ovum.
23; egg or ovum; sperm or spermatozoon; zygote
Meiosis occur during ___, the process by which germ cells, or ___, are produced.
gametogenesis; gametes
The normal human diploid number of chromosomes (___) is re-established
46
Time Period: from ovulation to fertilization
Ovum
Time Period: from fertilization to implantation
Zygote
Time Period: from implantation to 5-8 weeks
Embryo
Time Period: from 5-8 weeks until term
Fetus
Time Period: developing embryo or fetus and placental structures
Conceptus
Steps of Conception:
1. ___ transport
2. ___ transport
3. ___ and ___ development
4. ___ and ___ development
- Sperm Transport
- Egg Transport
- Fertilization and Zygote Development
- Implantation and Embryo Development
The sperm must be ___ and transported to the ___
deposited; site of fertilization
The sperm consists of a ___, ___ or mid-section/midpiece, and a ___.
head; body; tail
Each of these parts is equipped with ___ and ___ that allow the sperm as a whole to function properly
various molecules; smaller structure
A normal sperm head has a ___ and ___ shape
smooth; oval
This is the most important part of the cell given that it contains the nucleus
Sperm Head
This is a thin, elongated structure of the sperm
Tail
This is the central part of the sperm cell between the head and the tail
Mid-section/Midpiece
The mid-section makes up about ___ percent of the total sperm length
10%
The tail makes up about ___ of the entire sperm length
80%
The first step in egg transport is ___ by the uterine tube
capture of the ovulated egg
Ovulation must occur and the egg must be ___ by the ___
“picked up”; uterine tube
When inside the uterine tube, the egg is transported towards the ___, mainly as the result of contractions of the ___ of the tubal wall
uterus; smooth musculature
Egg transport occurs in two phases:
- Slow transport in the ___ for approximately ___
- More rapid phase for 8 hours during which the egg or embryo passes through the isthmus and into the uterus
Slow transport in the ampulla for approximately 72 hours
Tubal transport of the egg usually takes ___, whether or not fertilization occurs
3-4 days
Site of fertlization: ____ poriton of the ____
Ampullar portion of the fallopian tube
The union between the sperm and egg must result in the process of ___
Conception
Egg transport occurs in two phases:
- Slow transport in the ampulla for approximately 72 hours
- More rapid phase for ____ which the egg or embryo passes through the ____ and into the ____
More rapid phase for 8 hours during which the egg or embryo passes through the isthmus and into the uterus
This is the process by which a sperm fuses with an ovum to form a diploid cell or zygote
Fertilization
Other terms used to include: (3)
Conception, impregnation, fecundation
Preparation for Fertilization - High levels of estrogen cause:
- ____ within ____ helping ovum
- ____ of ____ facilitating movement of the sperm
- Peristalsis within fallopian tubes helping ovum
- Thinning of cervical mucus facilitating movement of the sperm
Preparation for Fertilization - Two layers of tissue surrounding the ovum’s cell membrane:
- cell membrane called ____
- gaseous corona called ____
Preparation for Fertilization - Two layers of tissue surrounding the ovum’s cell membrane:
- cell membrane called Zona Pellucida
- gaseous corona called Corona Radiata
Preparation for Fertilization - Ova considered fertile for about ____ after ovulation
Ova considered fertile for about 12-24 hours after ovulation
Preparation for Fertilization - Sperm can survive in female reproductive tract for ____ but are believed to be healthy for about ____
Sperm can survive in female reproductive tract for 48-72 hours but are believed to be healthy for about 24 hours
Sperm must undergo two processes before fertilization can occur: ____ and ____
Capacitation and Acrosomal Reaction
Capacitation is the removal of ____ and loss of ____
Plasma membrane; Seminal plasma CHON
Capacitation occurs in ____ and is thought to take about ____
Female reproductive tract; 7 hours
Acrosomal Reaction follows capacitation and is the process of ____ their enzymes to break down the ____ of the ovum
releasing; corona radiate
The Moment of Fertilization - occurs as ____
Nuclei unite
The Moment of Fertilization - ____ contains new combination of genetic material resulting in ____ from either parent and from anyone else
zygote; individual different
The Moment of Fertilization: ____ is determined
Sex of Zygote
Cellular Multiplication
Cleavage ➡️ Morula ➡️ Blastocyst
Implantation is the process that involving the attachment or ____, penetration or ____, and embedding or ____ of the blastocyst in the lining of the uterine wall
- Attachment or Apposition
- Penetration or Adhesion
- Embedding or Invasion
The frequent site of attachment for implantation is the ____ of the ____ uterine wall
Upper Part of the Posterior uterine wall
Under the influence of ____, the ____ increases in thickness and vascularity and is called the ____
progesterone; endometrium; decidua
Implantation occurs approximately ____ after fertilization
7-10 days
Implantation of a 7 1/2-day blastocyst in which the cells of the ____ are separated from the ____ by ____
embryonic disc; amnion; fluid-filled space
The erosion of the ____ by the ____ is ongoing
endometrium; syncytiotrophoblast
Implanatation is completed by ____, and the ____ is beginning to form a discrete layer beneath the ____
Day 9; extraembryonic mesoderm; cytotrophoblast
By ____, the embryo shows all the ____, a ____, and an ____
Day 16; three germ layers; yolk sac; allantois
allaintois collects liquid waste from the embryo
The ____ and associated ____ have become the ____, and ____ are developing
The cytotrophoblast and associated mesoderm have become the chorion, and chorionic villi are developing
the chorion and respective structures protect and nurture the embryo
Germ Layer: skin structures such as the epidermis, sweat glands, sebaceous glands, nails, and hair follicles
Ectoderm
Germ Layer: structures such as the lens of the eye and sensory epithelium
Ectoderm
Germ Layer: the pituitary and mammary glands
Ectoderm
Germ Layer: the central and peripheral nervous systems
Ectoderm
Germ Layer: oral structures such as the nasal cavity and the oral glands and tooth enamel
Ectoderm
Germ layer: the dermis
Mesoderm
Germ Layer: the wall of the digestive tract and urinary structures such as the kidneys and ureter
Mesoderm
Germ Layer: the musculoskeletal and cardiovascular system
Mesoderm
Germ Layer: the reproductive organs and connective tissues
Mesoderm
Germ Layer: structures such as the pleura, lymphatic tissue and cells, and the spleen
Mesoderm
Germ Layer: the respiratory tract epithelium except the nasal
Endoderm
Germ Layer: GI strucutures such as the lining of the digestive tract and the primary tissue of the liver and pancreas
Endoderm
Germ Layer: urinary structures such as the urethra and associated glands, urinary bladder, and vagina
Endoderm
This is the first and outermost embryonic membrane
Chorion
The chorion encircles the ____, ____, and ____
Amnion, embryo, and yolk sac
Amniotic fluid is slightly ____
Alkaline
The amnion originates from the ____ and is a thin protective membrane containing the ____
ectoderm; amniotic fluid
As the embryo grows, the ____ expands until it comes into contact with the ____ forming the ____
amnion; chorion; bag of water
The chorion develops from the ____ and has many finger-like projections called the ____
trophoblast; chorionic villi
Functions of the Amniotic Fluid:
1. Protects ____ againts ____
2. Control the embryo’s ____
3. Permits ____ external growth
4. Prevents ____ to the embryo-fetus
5. Allows ____
- Protects embryo againts mechanical injury
- Control the embryo’s temperature
- Permits symmetrical external growth
- Prevents adherence of the amnion to the embryo-fetus
- Allows freedom of movement
Contents of the amniotic fluid: (11)
- albumin
- uric acid
- ceratinine
- lecithin
- sphingomyelin
- bilirubin
- vernix
- leukocytes
- epethelial cells
- enzymes
- lanugo (fine hair)
The amount of amniotic fluid at 10 weeks is about ____
30 mL
The amount of amniotic fluid increases to ____ at 20 weeks
350 mL
After 20 weeks, the volume of amniotic fluid ranges from ____
700-1000 mL
A fetus swallows up to ____ every ____
600 mL every 24 hours
About ____ of amniotic fluid flows out of the ____ each day
400 mL; fetal lungs
This is the excessive amniotic fluid surrounding the fetus
Polyhydramnios
The yolk sac develops as a ____ in the ____ on about day ____ after conception
second cavity; blastocyst; day 8 or 9
The yolk sac provides source of ____ until the embryo’s hematopoietic system is mature
RBC
The ____ atrophies and remains as a thin white streak discrenible in the cord at birth
Yolk Sac
The umbilical cord is ____ in length and ____ in diameter or thickness
55 cm in length; 2 cm in diameter
The umbilical cord contains ____ that prevents pressure in the cord
Wharton’s Jelly
The placenta has two portions: the ____ and ____
Maternal Portion and Fetal Portion
After ____ weeks of gestation, the placenta is about ____ in diameter, ____ in thickness, and weighs approximately ____
20 weeks of gestation
* 15-20 cm in diameter
* 2.5-3 cm in thickness
* 400-600 grams
The umbilical cord contains 3 vessels: ____ umbilical vein and ____ umbilical arteries
1 vein, 2 arteries
The placenta is the means of ____ and ____ between the embryonic and maternal circulation
metabolic; nutrient exhange
The fetal portion consists of ____, with ____ apperance due to amnion
chorionic villi and their circulation; white and shiny
The maternal portion consists of ____; surface is ____
decidua basalis and its circulation; red and flesh-like
The development of the placenta begins with the ____
chorionic villi
Two trophoblastic layers appear, namely the ____ which is the outer layer, and the ____ which is the inner layer
- Syncytium - outer
- Cytotrophoblast - inner
The Syncytium is the ____ layer of the placenta and secretes the ____ of pregnancy
functional; placental hormones
The cytotrophoblast thins out and disappears about the ____, leaving only a single layer of ____ covering the ____
5th month; syncytium; chorionic villi
A third inner layer of connective mesoderm forms the ____
anchoring villi
The anchoring villi eventually forms the ____ that divide the placenta into ____ segments called ____
septa; 15-20 segments; cotyledons
The ____ in the cotyledons form a complex ____ structure
branching villi; vascular
____ invades the ____ of the endometrium, first opening the ____ and later opening the large ____
- Proliferaing trophoblast;
- decidua basalis;
- uterine capillaries;
- uterine vessels
By the ____ week, the placenta has began to function as a means of metabolic exchange
4th week
By ____, the placenta becomes a ____ organ
14th week; discrete organ
Fetal blood flows through the two ____ to the capillaries of the ____ then flows back through the ____ into the fetus
umbilical arteries; villi; umbilical vein
Late in pregnancy, ____ can be heard over the area of the umbilical cord
Funic Souffle
Maternal blood spurts from the ____ into the ____
spinal uterine arteries; intervillous spaces
A ____ is also heard just above the mother’s ____ during the ____ of pregnancy
uterine souffle; symphysis pubis; last months
____ are believed to facilitate placental circulation
Braxton Hicks contraction
called ‘false labor’ and are strong but irregular contractions
Placental Functions - The placenta has metabolic activities such as:
- producing ____, ____, and ____ for fetal use and hormone production
- breaking down ____ and ____
- storing ____ and ____
- producing glycogen, cholesterol, and fatty acids for fetal use and hormone production
- breaking down epinephrine and histamine
- storing glycogen and iron
Placental Functions - The placenta has transport functions such as: (4)
- diffusion
- facilitated diffusion
- active transport
- pinocytosis
pinocytosis is a type of endocytosis that absorbs small particles from the extracellular fluid
Placental Functions - The placenta produces horomones vital to the survival of the fetus, which include: (4)
- hCG
- progesterone
- estrogen
- hPL
hcg - human chorionic gonadotropin
hpl - human placental lactogen
Placental Functions - The placenta has immunologic properties. For instance:
1. The placenta and embryo appear ____ from immunologic reaction by the host
2. One theory suggests that ____ is immunologically ____ or protects antibody formation
- The placenta and embryo appear exempt from immunologic reaction by the host
- One theory suggests that trophoblastic tissue is immunologically inert or protects antibody formation
