Genetics, Embryology, and Human Development

gametogenesis

the process in which cells undergo meiosis to form gametes.

Spermatogenesis

- production of sperm

- a spermatogonium differentiates into two sperm: 23X and two sperm 23Y

Oogenesis

- The production of mature egg cells

- oocyte does not complete 2nd meiotic division until after fertilization

- secondary oocyte: 23X

fertilization

- secondary oocyte surrounded by several sperms

- a sperm has entered the oocyte causing a mature oocyte to form

- a zygote has formed containing 46 chromosomes (diploid number)

Down Syndrome (Trisomy 21)

a genetic disorder caused by three copies of chromosome 21 in each cell, for a total of 47 chromosomes per cell

Turner Syndrome

a genetic disorder caused by only having one copy of the X chromosome in every cell, for a total of 45 chromosomes per cell

Week 1 of embryonic development

- pre-implantation embryo moves through oviduct to surface of uterus endometrium as blastocyst with inner cell mass

- growth is achieved by mitosis

- complexity is achieved through morphogenesis and differentation

Week 2 of embryonic development

- amniotic cavity appears

- embryoblast differentiates into the epiblasts and hypoblasts

epiblast

the outermost layer of an embryo before it differentiates into ectoderm and mesoderm.

hypoblast

forms yolk sac

human embryonic stem cells are

pluripotent

pluripotent cells are capable of

these type of cells are capable of

- self renewal

- able to differentiate into specialized cell types

What determines the choices of what a pluripotential cell becomes?

Responses to cues from immediate surroundings

What achieves architectural precision and coordination in organ interactions?

Interactions of organs

What is the term for the process by which one cell influences the fate of another?

Induction

How does the mechanism of signal transfer vary in pluripotential cells?

It appears to vary within the specific tissues involved

What do most inducible tissues pass through during development?

A transient but sharply delimited physiologic state

What can cause failure of an inductive interaction in an interacting system?

A delay in development of one or more components

induction

the interaction that lead to a change in the course of development of at least one of the interactants

weeks 3 -6 of embryonic development

- primitive streak forms

- notochrodal canal develops openings --> notochordal plate --> folds into the notochord--> structural basis for the vertebral column

- neural plate forms and folds

- primordial CVS forms

Week 4 of embryonic development

- heart begins to beat

- folding of embryo

- heart position moves more ventrally

- brain position moves more cranially

Three germ layers

ectoderm, mesoderm, endoderm

ectoderm consists of

what germ layer consists of

- CNS

- PNS

- skin

mesoderm consists of

what germ layer consists of

- musculoskeletal

- heart

- kidneys

- connective tissue/muscle of viscera

endoderm consists of

what germ layer consists of

- epithelial lining of digestive and respiratory tract

week 7-10 of embryonic development

- external genitalia begins to differentiate

- genitalia has male or female characteristics

Week 11 of embryonic development

babies bone begins to harden

babies between 26 to 28 weeks have difficulty surviving because

between what weeks do babies have difficulty surviving because the respiratory system and the central nervous system are not completely differentiated

neuralation

formation of neural plate and neural tube

- cranial 2/3 represents the future brain

- caudal 1/3 represents the future spinal cord

neural tube

this structure differentiates into the CNS

- rostral neuropore

- caudal neuropore

neural crest

- this structure gives rise to cells that form most of the PNS and ANS

- development of spinal meninges

neuroblasts

immature neurons

glioblasts

give rise to macroglial cells and microglia cells

macroglial cells

astrocytes

- blood brain barrier

- axon guidance

oligodendrocytes

- myelination

microglia

phagocytes

- white blood cell that ingest invading microbes

3 primary vesicles

prosencephalon, mesencephalon, rhombencephalon

5 secondary vesicles

telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon

Telencephalon

cerebral hemispheres (lateral ventricles)

Diencephalon

thalamus and hypothalamus (3rd ventricle)

Mesencephalon

midbrain (aqueduct)

metencephalon

pons and cerebellum (upper part of 4th ventricle)

Myelencephalon

medulla oblongata (lower part of 4th ventricle)

fetal circulation

- blood is oxygenated in the placenta

- oxygenated blood delivered from placenta to umbilical vein

- de-oxygenated blood returned to placenta via umbilical arteries

endochondral ossification

process in which bone forms by replacing hyaline cartilage

myoblasts

Embryonic cells that fuse to form muscle fibers

- myo = muscle

- blast = immature precursor or "maker" cell

pharyngeal arch mesenchyme

head and neck muscles are derived from this type of mesechyme

splanchnic mesoderm

cardiac muscle and most smooth muscle are derived from this mesoderm

Viscera are innervated by

the ANS innervates what

Mosonomy

missing a chromosome

trisonomy

extra chromosome

teratogen

any factor that can cause a birth defect

organogenetic period

critical period of human prenatal development

- weeks 4-8

- teratogens may induce major birth defects

physiologic defects

critical period of human prenatal development

- functional disturbances such as mental deficiency are likely to result from disruption of development during the fetal period

neural tube defects

most defects result from failure of fusion of one or more neural arches of the developing vertebrae

- affects the tissues overlying the spinal cord

spina bifida occulta

- unfused neural arch

- associated with a tuft of hair

spina bifida with meningocele

- cyst with meninges and CSF

spina bifida with meningomyelocele

- cyst with meninges, CSF, and spinal cord

spina bifida with myeloschisis

- exposed spinal cord

encephalocele

herniation of brain tissue

Meningoencephalocele

herniation of the meninges and part of the brain

Meningohydroencephalocele

herniation of meninges, part of the brain, and part of the ventricular systems

meroencephaly

acrania: partial absence of the brain

microephaly

underdeveloped brain

hydrocephalus

excess accumulation of fluid (CSF) in the brain

Arnold-Chiari malformation

herniation of cerebellum and brainstem through foramen magnum

patent foramen ovale

Failure of foramen ovale to close after birth.

- more common in females

ventricular septal defects

most common type of CHDs

- results in dyspnea and cardiac failure early in infancy

Tetralogy of Fallot

congenital malformation involving four distinct heart defects

- pulmonary artery stenosis (obstruction of right ventricular outflow)

- ventricular septal defect

- dextroposition of the aorta (aorta straddling over interventricular septum)

- right ventricular hypertrophy

cyanosis

deficient oxygenation of blood