Module 12 - Development and Inheritance Flashcards
Gestation
Gestation – full time in development – 38-40 weeks
Embryonic Period
Embryo – weeks 3-8
End week 8, all major systems have developed from the 3 primary germ layers
Through processes of neurulation and organogenesis
Non-functional or semi functional
Placenta is functional
Embryonic membranes are formed
Looks human
Fetal Period
Fetus – week 9 till birth – 30 weeks
Cell growth & differentiation
Stages of Pregnancy
Stages of Pregnancy
Fertilization
Implantation
Embryonic growth
Fetal Growth
Birth
Fertilization
Fertilization
Occurs in uterine tubes
Sperm survive 3-5 days – Oocyte survives 24
Sperm and oocyte combine and nuclei of each haploid fuse – diploid cell
Fertilization membrane prevents other sperm – hardens zona pellucida
Meiosis of oocyte resumes to form Zygote
Capacitation
Capacitation – priming sperm – proteins and cholesterol on top of acrosome membrane – keeps ridged – protection
fluids from female deplete cholesterol on heads of sperm to aid motility
thins membrane so lysosomal enzymes can release once egg is penetrated
Oocyte Cell Layers
Oocyte has two cell layers – sperm must penetrate
Corona radiata – 100s of sperm hit this membrane
Sperm have spontaneous acrosomal reaction – degrades the wall
Zona pellucida – on contact – sperm bind to receptors
Sperm starts acrosomal reaction – enzyme breakdown
Fertilization membrane prevents other sperm – hardens zona pellucida
Zygote
Zygote – new diploid cell – half gene material from mom and dad
Conceptus
Conceptus – Zygote and membranes
Cleavage
Cleavage – rapid mitotic cell division within Conceptus
Blastomeres – cells produced by cleavage
Early divisions of the zygote that occur without an increase in cell size.
Morula
Morula – 16-cell conceptus reaching uterus – solid mass of cells
A morula is a solid ball of cells caused by cleavage divisions
Blastocyst
Blastocyst – whole cell – travels into uterus – small fluid filled sac
Trophoblast - Future embryonic membranes & placenta
Embryoblast – inner cell mass – baby – onside of cell
Blastocoel – internal fluid-filled cavity
Implantation
Implantation
Blastocyst is free in uterus
End of 1st week – it will attach to the uterine wall
Fundus or posterior wall
Ectopic pregnancy – implants outside uterus
Blastocyst implants in the endometrium
Trophoblast cells fuse together – form syncytiotrophoblasts
Trophoblast secrets human chorionic gonadotropin (hCG)
Uterine wall builds up around blastocyst
Implantation is complete by middle of 2nd week
human chorionic gonadotropin
Trophoblast secrets human chorionic gonadotropin (hCG)
Tells corpus luteum to stay
keeps secretion progesterone & estrogen
Mimics LH – keeps attachment of fetus to lining of uterus
Stims male fetal gonads to secrete testosterone
Syncytiotrophoblast
Syncytiotrophoblast – Digests lining of endometrial cells to firmly secure
Embryonic Disc
Embryonic Disc – Inner mass cells form two-layered disc of cells and a space – bilaminar disc
Epiblasts
Hypoblasts
Amniotic cavity – space
Epiblasts
Epiblasts – Cells of upper layer – develops internal cavity – Amniotic cavity – creating Amnion
Hypoblasts
Hypoblasts – Cells of lower layer – form yolk sac
Replace blastocyst cavity
Yolk Sac
Yolk sac – developed from blastocyst cavity – hypoblasts
Supplied nutrients absorbed from trophoblast
Beginning of blood circulation
Amnion
Amnion – protective membrane – epiblasts
Overlies embryonic disc
Fills with amniotic fluid
Shock absorber & regs temp
Grows to surround embryo
Allantois
Allantois – finger projections from yolk sac
Vascularized membrane – site of blood formation
Primitive excretory duct – becomes uterine bladder
Chorion
Chorion – outer membrane
Becomes placenta
Develops stalk – becomes umbilical cord
The chorion is the outermost of the embryonic membranes that surrounds the fetus and becomes the embryonic part of the placenta.
Germinal Layers of Embryo
Germinal Layers of Embryo
Inner cell mass development – gastrulation – develop 3 layered discs
Blastocyst differentiate into germ layers – form all tissues and organs
Ectoderm - head
Mesoderm – main body
Endoderm – inside stuff
Ectoderm
Ectoderm – head parts
Replace epiblast
Nervous systems, sensory
organs, epidermis, hair,
and nails
Mesoderm
Mesoderm – main body – support
structures and muscle
Push in b/w layers of
bilaminar disc
Skeleton, muscles, connective tissue, heart, blood vessels, and kidneys
Endoderm
Endoderm – inside stuff
Replace hypoblasts
Epithelial lining of GI tract, liver, pancreas, and lungs
Placenta - Functions
Placenta - Functions
Secretes – hCH, estrogen & progesterone – maintain and stim development
Oxygen and CO2 transport – lungs
Blood doesn’t mix – acts as a blood filter – no cells pass – placental membrane
Stores nutrients – carbohydrates, proteins, Ca+, Iron
Excretes and filters waste
Mediates diffusion of glucose, amino acids, fatty acids, vitamins, and minerals
Protection – Microorganism and viruses cannot cross but drugs & alcohol pass
Placenta - Development
Developed by 3rd month – formed by chorion and part of endometrium (decidua basalis)
Syncytiotrophoblasts form chorionic membrane – envelops conceptus – invades uterine walls
Chorionic villi
Chorionic villi
Chorionic villi – finger projections – fetal portion – root in endometrium – separation from mom
Ample surface area 4 exchange b/w mom & baby
Umbilical cord
Umbilical cord – vascular connection from placenta to fetus
Two umbilical arteries – deoxygenated fetal blood to placenta
One umbilical vein – Oxygenated blood from placenta to baby
Mucous connective tissue (Wharton’s jelly)
Fetal Period
Fetal Period
Weeks 9-38 (birth)
Cell growth and differentiation
Sexual differentiation
Fetal Circulatory System
Growth of Organ Systems
Fetal Circulatory System
Fetal Circulatory System
Integrated with placenta via umbilical cord
Receives O2 and nutrients from
placenta
Circulatory system needs reconfiguration at birth
Shunts
Shunt
Shunt – circulatory shortcut that diverts flow of blood from one region to another
Shunts are not needed after birth
Ductus Venosus Shunt
Ductus Venosus Shunt – bypass immature liver
Liver is semi functional – doesn’t need much blood
O2 blood flows from umbilical vein towards inferior vena cava – bypasses liver – towards heart
Becomes ligamentum venosum
Foramen Ovale
Foramen Ovale – lung bypass
Fetal lungs non-functional – placenta regulates O2 and CO2
Allows O2 blood in right atrium to left atrium
Mixes with now CO2 blood returning from pulmonary circuit
Blood moves into left ventricle – pumped into aorta
Avoids pulmonary trunk
Becomes fossa ovalis
Ductus Arteriosus
Ductus Arteriosus – away from lungs to aorta
Blood from right ventricle to aorta
Within pulmonary artery – diverts a portion of blood into aorta
Becomes ligamentum arteriosum
Corpus Luteum to placenta
3-4 months – Corpus luteum secretes progesterone and estrogen
Maintain uterine lining
Prevents ovulation – suppress FSH and LH
Preps mammary glands to secrete milk
Placenta takes over – corpus luteum degrades
Secrets estrogen, progesterone, hGH, and relaxin
Estrogen
Estrogen
Suppresses FSH and LH
Induces growth of fetal tissue
Regulates progesterone produce and triggers synthesis of cortisol
Helps with maturation of lungs, liver, and endocrine organs
Stims maternal tissue growth
Uterine enlargement
Mammary duct expansion and branching
Relaxin
Relaxin
Preps mom’s body for birth
Increases elasticity of symphysis pubis joint and pelvic ligaments
Allows expansion for birth
Dilates cervix during labour
Progesterone
Progesterone
Suppresses FSH and LH
Inhibits uterine contractions – no premature birth – protection
Decreases later – allows contractions for labour
hPL – human placental lactogen
hPL – human placental lactogen
breast development
protein anabolism
catabolism of glucose and fatty acids
CRH – Corticotropin-releasing hormone
CRH – Corticotropin-releasing hormone
Clock – establishes time of birth
Anterior Pituitary Gland increases ??
Anterior pituitary gland enlarges
Ramps up hormone production – increases hormone levels
Thyrotropin
Prolactin
ACTH – adrenocorticotropic hormone
Parathyroid hormone increases
Thyrotropin
Thyrotropin – increase thyroid hormone – increases mom’s metabolic rate
Prolactin
Prolactin – stims mammary gland enlargement
ACTH – adrenocorticotropic hormone
ACTH – adrenocorticotropic hormone – stims maternal cortisol section
Contributes to fetal protein synthesis
Parathyroid hormone
Parathyroid hormone increases – mobilizes calcium from maternal bones for fetal use
Maternal Anatomic and Physiological Changes
Maternal Anatomic and Physiological Changes
Weight gain
Increase protein, fat, mineral storage
Breast enlargement
Lower back pain – pressure – organs moving
Cardiovascular changes
Increase appetite
Nausea, vomiting, heart burn, motility decreases
Urinary
Pressure increases frequency and urgency
Glomerular filtration rate increases – increased blood and filter needs
Cardiovascular changes in Mom
Cardiovascular changes
Increases stroke volume, cardiac output, and blood volume
Needs to increase volume for baby
Stroke and output – combat pressure increase at placenta
Pulmonary function increases
Expels more CO2 from baby’s waste
Needs more O2 for baby
Labour
Labour – process of expelling fetus from uterus
through vagina
Parturition – giving birth
Progesterone levels plateau and allow for uterine
contractions
Braxton Hicks contractions
Braxton Hicks contractions – irregular peristaltic contractions – false labour
True labour
True labour – stretching of myometrium and cervix –
fetus head down – stims uterine contractions
Stages of Birth
Stages of Birth
Dilation of cervix
Expulsion of fetus
Delivery of placenta – after birth
Dilation of cervix
Dilation of cervix – Onset labour to complete dilation
Amniotic membranes rupture – water breaks – pressure form fetal head – moves down
Fully dilated – 10cm
Longest stage – 6-12 hrs
Expulsion of fetus
Expulsion of fetus – Complete cervical dilation to delivery
Fetal head enters birth canal
Ends with baby out
After Birth
Delivery of placenta – after birth
Placenta expelled by uterine contractions
Contractions also constrict blood vessels inside – reducing hemorrhage risk
Genetics
Genetics – branch of biology that deals with inheritance
Inheritance
Inheritance
Passing of hereditary traits from one generation to another
Diploid Number
Diploid number (2n)
1 chromosome in each pair comes from mom and dad
Karyotype
Karyotype – systematic arrangement 1-23
Gene
Gene – section of DNA in specific location on a chromosome that contains information that determines a trait
Genotype
Genotype – complete genetic makeup
Phenotype
Phenotype – characteristics that genes express – punnet square
Physical, behavioural, and biochemical
Genomic imprinting – phenotype is very different
Influenced by alleles of genes present, other genes and environ.
Homologous chromosomes
Homologous chromosomes
Make up complementary pair – same gene characteristics in same location on chromosomes
Two chromosomes in a pair, contain genes that control same trait
Heterozygous
Heterozygous
Different genes on homologous chromosomes – different traits
Two different versions of the same gene from each parent – W or w
Dominant gene
Dominant gene – W – masks another – trait expressed both in homozygous and heterozygous form – only need a single copy – Ww
Incomplete dominance
Incomplete dominance – genetic pattern where two alleles blend to create new phenotype – Red and white = pink
Recessive gene
Recessive gene – w – trait only expressed in homozygous form – masked in heterozygous form – must have two copies – ww
Allele
Allele – one copy of gene
inherited from each parent – may very in complementary pairs
two genes coding same trait, in some position on homologous chromosomes
Multiple-allele inheritance
Multiple-allele inheritance – gene has more than two alternate forms
ABO blood groups & Hair colour – brown, blonde, or red
Polygenic inheritance
Polygenic inheritance
Inherited trait combines effects – Skin colour
Mutation
Mutation – permanent heritable change – different and new effect
multiple-allele inheritance
Sex chromosomes
Sex chromosomes – 23 – determines sex – most traits on here – gender linked genes
Females – XX
Males – XY
Males control sex by sending either X or Y in haploid cell of sperm
Responsible for gender and some nonsexual traits
Autosomal chromosomes
Autosomal chromosomes
22 of 23 pairs – homologous chromosomes look alike and have same appearance in males and females
Carries 100s-1000s of genes, each code for assembly of particular protein
Genes are expresses as proteins
Sex-linked or X-linked Traits
Sex-linked or X-linked Traits
Some genes appear on X chromosomes and not on Y
Sex-linked or X-linked traits
X chromosome is longer so it holds more genes
Sex Differentiation - Males
Males
Bipotential gonads into testis and epididymis
Mullerian duct degenerates
Wolffian ducts become ductus deferens
Cloaca becomes urethra and rectum
Sex Differentiation - Females
Female
Bipotential gonads into ovaries
Wolffian ducts degenerate
Mullerian ducts become uterine tubes and uterus
Cloaca divides into vagina, urethra and rectum
