Chapter 29: Development And Ingeritance Flashcards
Prenatal Development
Is the time from fertilization to birth and includes the embryonic and fetal periods.
Is divided into periods of 3 calendar months known as trimesters.
Trimesters
Hormonal changes occurs during all 3 of the stages
1st : most critical stage of development. All major organs systems begin to form. Priory when the developing organism is most vulnerable to effects of drugs, etc.
2nd: characterized by the nearly complete development of organ systems. By the end, fetus assumes distinctively human features.
3rd: period of fetal growth in which the weight doubles. Most organs become fully functional.
Embryonic Period
Extend from fertilization through the 8th week.
Major body’s organs and systems develop.
Includes fertilization, cleavage of zygote, blastocyst formation and implantation.
Blastula formation occurs.
Acrosomal Reaction
The release of the contents of acrosome. The acrosome enzymes digest a path through zonal pellucida as the lashing sperm tail pushes the sperm cell onward.
Polyspermy
Fertilization by more than one sperm cell.
Male Pronucleus
Developed from the nucleus in the head of the sperm.
Female Pronucleus
Developed from the nucleus of the fertilized ovum.
Syngamy
The process where a male and female pronuclei form and fuse producing a single diploid nucleus.
Fusion of haploid pronuclei restores the diploid number (2n) of 46 chromosomes/
Zygote
Fertilized ovum
Results from the fusion of the male pronucleus and the female pronucleus.
Dizygotic Twins
Produced from the independent release of 2 secondary oocytes and subsequent oocytes.
Subsequent fertilization of each different sperm.
Monozygotic Twins
Develop from a single fertilized ovum.
Contain exactly the same genetic material and are always the same sex.
Cleavage
After fertilization, rapid mitosis cell divisions of the zygote takes place.
Blastomeres
Progressively smaller cells that are produced by cleavage.
Morula
A solid sphere of cells produced by successive cleavage.
Surrounded by the zonal pellucdia and is about the same size as the original zygote.
Uterine Milk
Fluid, and nutrients that is stored in the cytoplasm, of the blastomeres of the morula.
Provides nourishment for the developing morula.
Blastocyst Cavity
Large fluid filled cavity.
At the 32 cells stage, fluid enters the morula and collects between the blastomeres. They are reorganized in this cavity.
Once the cavity is formed the mass is called a blastocysts.
Blastocyst.
Developing mass that is formed in the blastocyst cavity.
It has hundreds of cells and is about the same size as the original zygote.
During formation 2 distinct cells population arises”
1. Embryo blast
2. Trophoblast
Embryoblast
Or inner mass
Internally located and eventually develops into the embryo.
Trophoblast
Is the outer superficial later of cells that forms the sphere like wall of the blastocyst.
Promotes implantation and produces hCG
Will develop into the outer chorionic sac that surrounds the fetus and the fetal portion of the placenta.
Develops about 8 days after fertilization into 2 layers in the region of contact between the blastocyst and endometrium.
Implantation
Blastocyst remains free with the uterine cavity for 2 days before it attaches.
6 days after fertilization the blastocyst loosely attaches to the endometrium.
Implants is either the posterior portion of fundus or the body of the uterus.
Orients with the inner cell mass towards the endometrium.
Decidua
Following implantation the endometrium becomes this.
Separates from the endometrium after the fetus is delivers much as normal menstruation.
Regions:
Development of Bilaminar Embryonic Disc
Cells of the embryoblast differentiate into 2 layers around 8 days after fertilization.
Amniotic Cavity
A small cavity that appears after development of the bilaminar embryonic disc within the epiblast and eventually enlarges to form the cavity.
Amnion
Developed from the epiblast
Is a profile layer
As the amniotic cavity enlarges a single layer of squamous cell forms this dome like roof above the epiblast cells.
Amniotic Fluid
Fluid that fills the amniotic cavity.
Derived from maternal blood.
The fetus contributes to the fluid by excreting urine into the cavity.
Once baby is delivered the baby can breathe on its own, absorbing the fluid in the lungs.
Functions:
1. Serves as shock absorber for the fetus,
2. helps regulate fetal body temp
3. helps prevent the fetus from drying out
4. prevents adhesions between skin of the fetus and surround tissues.
Development of the Yolk Sac
On the 8th day after fertilization, cells at the edge of the hypoblast migrate and cover the inner surface of the blastocyst wall.
The migrating columnar cells become squamous and form the thin membrane called exocoelomic membrane.
Together with the hypoblast and membrane from the wall of the yolk sac.
Development of Sinusoids
Occurs on the 9th day after fertilization.
Blastocysts becomes complete in GH embedded in the endometrium.
As the syncutiotroblast expands, small spaces called lacunae develop within in.
After 12th day, lacunae fuse to form larger spaces called lacunae networks.
Endometrial capillaries around the developing embryo become dilated as maternal sinusoids.
Extraembryoinc Mesoderm
Develops on about the 12th day after fertilization.
These cells are derived from the yolk sac and form a CT layer around the amnion and yolk sac.
Chorion
Formed by the extraembryonic mesoderm, together with the 2 layers of the trophoblast.
Surrounds the embryo and later the fetus.
Becomes the principle embryonic part of the placenta.
Protect the embryo and fetus from the immune response of the mother.
Chorionic Cavity
When the inner layer of the chorion fuses with the amnion.
Connecting Stalk
The future umbilical cord.
By the end of the 2nd week of development the bilaminar embryonic disc becomes connected to the trophoblast by a band of extraembryonic mesoderm known as the connecting stalk.
Gastrulation
The fist major event of the 3rd week of development.
Occurs about 15 days after fertilization.
The bilaminar embryonic disc transforms into a trilamionar embryonic disc consisting of 3 layers:
1. Ectoderm-inside
2. Mesoderm-middle
3. Endoderm-outside
Primitive Node
A rounded structure that is formed at the head end of the primitive stalk as small group of epiblastic cells.
Notochordal Process
Occurs about 16 days after fertilization.
Mesodermal cells from the primitive node migrate towards the head of the embryo and follow tube of cells in the midline.
Notochord
Notochordal process becomes a solid splinter of cells that occurs by 22-24 days or third week of development.
Nuurulation: the process by which the neural plate, neural fold and neural tubes form.
Neurulation
Process where the neural plate, neural fold and neural tube are formed
1. Notochord included ectodermal cells over it to form the neural plate.
2. The neural fold forms by the end of the 3rd week. Lateral edges of the neural plate becomes more elevated.
3. Neural groove is the depressed mid region.
4. Neural tube occurs when the neural folds approach each other and fuse.
Chorionic Villi
Development begins by the end of the 2nd week.
Finger like projections that consist of chorion.
By the end of the 3rd week, blood capillaries in the uterine wall develop into the villi.
Intervillous Spaces
Formed by fetal capillaries with the chorionic villi that project into lacunae.
These spaces bathe the chorionic villi with maternal blood.
Placentation
The process of forming the placenta.
Placenta
Contains chorionic vill that is the site of exchange of nutrients and waster between the mother and fetus.
Produces hormones to sustain the pregnancy.
Has 2 distinct parts:
1. Fetal portion: formed by the chorionic villi of the chorion
2. Maternal portion: formed by the Decidua basalis of the endometrium.
When fully developed is shaped like a pancake.
Wharton’s Jelly
Supporting mucous CT.
Derived from the allantois.
Umbilical Cord
The actual connection between the placenta and embryo. Later the fetus.
Developed from the connecting stalk
2 cm wide and 50-60 cm long.
Afterbirth
After birth the placenta detaches from the uterus and is delivered.
Umbilicus
Scar or navel that was where the cord was attached to the baby.
It becomes a thin later of skin and scar tissue forms.
Fetal Period
From the 9th weeks until birth
Tissue and organs that developed during the embryonic period grow and differentiate.
The fetus is less vulnerable to the damaging effects of drugs, radiation and microbes than when it was an embryo.
Embryonic Period
1-4 weeks, size and weight 0.6 cm
Primary germ layer and notochord develop.
Neurulation occurs
Primary brain vesicles, somites and intraembryonic coelom develop.
Blood vessel formation begins and blood forms in yolk sac, allantois and chorion.
Heart forms and begin to beat.
Chorionic villi develop and placental formation begins.
The embryo folds.
Primitive gut, pharyngeal arches and limb buds develop.
Eyes and ears begin to develop, tail forms and body systems begin to form.
Hormones of Pregnancy
- Progesterone and estrogen are secreted by the corpus luteum in the ovary.
Maintain the lining of the uterus during pregnancy and prepare the mammary glands to secrete milk. - Human Chorionic Gonadotropin (hCG) is secreted by the chorionic of the placenta into blood.
Stimulates the corpus luteum to continue production of progesterone and estrogen. - Relaxin is produced first by the corpus luteum of the ovary then by the placenta.
Increases flex ability of the pubic symphysis and joints to help dilate the uterine cervix. - Human Chorionic Samatomammotropin (gCS), helps prepare mammary glands for lactation, enchases growth by increasing protein synthesis, decrease glucose use and increases fatty acid use for ATP production
- Corticotropin-Realsesing Horome establishes the timing of birth, increase secretion of cortisol.
Corticotropin-Releasing Hormones (CRH)
Produced by the placenta.
In non pregnant people is secreted only by the neuro secretory cells in the hypothalamus.
Is thought to be part of the clock that establishes birth.
Labor
The process by which the fetus is expelled from the uterus through the vagina.
Also known as parturition.
True Labor
Occurs when uterine contraction are at regular intervals.
Has 3 stages:
1. Stage of dilation: time from the onset of labor to the compete dilation of the cervix. Lasts 6-12 hours. Features reg contractions
2. Stage of expulsion: the time from complete cervical dilation to delivery of the baby.
About 10 mins to several hours.
3. Placental stage: the time after delivery until the placenta or afterbirth is expelled by powerful uterine contractions. About 5-30 mins.
Puerperium
Occurs following the delivery of the baby and placenta.
A 6 week period where the organs and physiology return to the pre-pregnancy state.
Involution
A process where tissue catabolism occurs.
The uterus is decreased in size especially in lactating women.
Lochia
Occurs 2-4 weeks after delivery.
Uterine discharge that consists of blood and serous fluid from the former site of the placenta.
Lactation
The production and ejection of milk form the mammary glands.
Prolactin (PRL)
Principal hormone in promotion milk production.
Is secreted from the anterior pituitary gland.
Milk Ejection Reflex
Caused by oxytocin to release milk into the mammary ducts.
Milk is formed by the gland at cells of the breast and is spotted until the baby begins active sucking.
Colostrum
Occurs the first few days after birth. Mammary glands secrete this cloudy fluid.
Not as nutritious as milk. Contains less lactose and no fat.
Serves adequately until the appearance of true milk.
Chorionic Sac
Formed by the trophoblast.
Surrounds the fetus and fetal portion of the placenta.
Primary Germ Layers
Formed from epiblast and hypoblast that transforms into trilaminar embryonic discs that consists of 3 layers.
Major embryonic tissues from which the various tissues and organs of the body develop.
3 layers:
1. Ectoderm
2. Mesoderm
3. Endoderm
Ectoderm
Outside germ layer of embryonic tissue.
Consists of epi composed of tightly packed cells
Becomes epi of the skin and nervous system.
Mesoderm
Middle germ layer of embryonic tissue
Composed of loosely organized CT called mesenchyme.
Gives rise to muscles, bone, other CT
Endoderm
Inside germ layer of embryonic tissue
Epi composed of tightly packed cells
Bnecomes lining of the GI and Resp tract
Fertilization
Occurs within the fallopian tubes
Capacitation
Series of functional changes that sperm go though when they are in the female reproductive tract.
Decidua Layers
- Decidua basalis: portion of endometrium between embryo and stratum basalis of uterus.
- Decidua capsularis: portion of endometrium located between the embryo and the uterine cavity
- Decidua parietalis: is the remaining modified endometrium that lines the non involved areas of the rest of the uterus.
Somite
Differentiate into dermatome
Progesterone
This hormone must be eliminated completely for labor to take place.
Pregnancy Stoke Volume
Stoke volume can increase by 30 % during pregnancy.
Ductus Venosus
Connects the umbilical vein to the inferior vena cava in infants.
Shuts off once the lungs begin to function due to the contraction of smooth muslce in its walls.
Once the baby is born this collapses, closes around 3 months after birth.
Oxytocin
Principle horome that release milk into mammary ducts
Changes of the Body Associated with Pregnancty
Airway resistance declines by 30-40%
Delayed gastric emptying
Decreases GI tract motility
Stress incontinence
Stimulus for Maintaining Prolactin during Lactation
This is stimulated by sucking of the infant.
Stretch receptors ion the nipple are activated which stimulated the anterior pituitary to secrete more prolactin.
Labor
Or partition
Process by which the fetus is expelled from her uterus through the vagina.
True Labor
Begins when uterine contractions occur at regular intervals, usually produces pain.
There is show (discharge of blood contains muscular into the cervical canal) and cervix dilates.
False Labor
Pain is felt in the abdomen at irregular intervals.
Does not intensify and walking does not alter the pain.
There is no show or cervical dilation.
3 Stages of Labor
- Stage of dilation: onset of labor to the complete dilation of the cervix. Last 6-12 hours. Regular contractions happen.
- Stage of expulsion: the time from complete cervical dilation to delivery of the bay. 10-mins to several hours.
- Placental stage. The time after delivery until the placenta or afterbirth is expelled by powerful uterine contractions. About 5-30 mins.
Neonatal Period
28 days after birth.
Neo mean new and natal means birth.
Edema in Pregnancy
The enlarges uterus causes compression of the inferior vena cava causes decrease venous return leading to edema in the lower limbs and may produce varicose veins.
Skin Changes with Pregnancy
Chloasma: pigmentation around the eyes and check bones
Linea nigra: darkened line that appears in the abdomen.
Areolae of the breasts may have increased pigmentation
Respiratory Changes with Pregnancy
Tidal volume increase 30-40%
Expiratory reserve volume decreases
Functional residual capacity decreases
Airway resistance decreases
Fetal Period
The time from the 9th week of gesteration until birth.
Tissue and organs that developed during hte embryonic period grow and differentiate.
Characterized by explosive body growth.
Newborn Breathing
Full term baby breathes about 45 times per min and gradually decreases as baby ages.
If resp rate is 60 or greater, the baby is likely losing OC2.
Foramen Ovale
Closure occurs the moment of birth due to the folding of two flaps of tissues and diverts deO2 blood to the lungs for the first time.
Respiratory Changes with Newborn
When the baby is born the blood supply from the mother ends, causing CO2 to build up in the baby’s blood.
This action stimulates the medulla Oblongata causing the baby to take its first breathe.
Path of Sperm Cell
To fertilize the second at oocyte sperm cell must penetrate:
Corona radiate (first outer layer, contains translocation cells), zona pellucida (clear glycoproteins layer between corona radiate and oocyte PM), plasma membrane of the secondary oocyte, cytoplasm of the secondary oocyte.
Puerperium
6 week period after deliver of baby and placenta.
During this time the uterus see a reeducation is size called involution, the uterine discharge is called lochia.
The elasticity of the cervix decrease and it returns to it pre pregnancy state.
Embryonic Period 1-4 Weeks
Primary germ layers form
Notochord develops.
Neurulation occurs.
Primary brain vesicles, somites and intraebryonic coelom develop.
Blood vessel formation begins and blood forms in your sac, allantois and chorion.
Heart forms and begin to beat.
Chorionic villi develop and placental formation begins.
Embryo folds
The primitive gut, pharyngeal arches and limb bud develops.
Eyes and ear begin to develop, tail forms and body system begin to form.
Embryonic Period 5-8 Weeks
Limbs become distinct and digits appear.
Heart become 4 chambers.
Eyes are far apart and eyelids are fused.
Nose develops and is flat.
Face is more human like.
Bone formation begins.
Blood cells stat to form in the liver.
Evertail genitals negion to diggerentiate.
Tail disappears.
Major blood vessel form.
Many internal organs continue to develop.
