Chapter 3: Embryogenesis and Development

Determinate Cleavage

Refers to cells that once divided have a plan for what they will differentiate into

Indeterminate Cleavage

Refers to cells that once divided could become anything

What are the stages of development from zygote to gastrula

Zygote → 2- 4- 8- 16-cell embryo → Morula → blastula → Gastrula

What stage does implantation occur?

Implantation occurs during the blastula stage

what forms from the Ectoderm

Integumentary, lens of eye, nervous system, inner ear

what forms from the Mesoderm

Musculoskeletal system, circulatory system, excretory system, gonads, muscular and connective layers of digestive and respiratory system, adrenal cortex

what forms from the Endoderm

Epithelial linings of digestive system and respiratory system, parts of liver, pancreas, thyroid, bladder, and distal urinary and reproductive tracts

What is induction

Nearby cells influence the differentiation of adjacent cells which ensures proper spatial location

What tissues do neural crests cells develop into

Neural crest cells become the PNS

Determination vs Differentiation

Determination is a commitment of a cell to a particular lineage and differentiation refers to the actual changes that occur for the cell to assume the structure and function of the determined cell type

Totipotent

Cell can develop into any type of cell

Pluripotent

Cell can develop into anything other than placental structures

Multipotent

can develop into into multiple types of cells within a particular lineage

Autocrine

signal acts on the same cell that secreted it

Paracrine

signal acts on local cells

Juxtacrine

Cell triggers adjacent cells through direct receptor stimulation

Endocrine

signal travels via the bloodstream to act at distant sites

Apoptosis

programmed cell death that results in blebs of dead cell that get digested

Necrosis

cell death due to injury and results in spilling of cytoplasmic contents

Umbilical arteries

carry deoxygenated blood from the fetus to the placenta

Umbilical Veins

carry oxygenated blood from the placenta to the fetus

Foramen Ovale

connects right atrium to left atrium and bypasses the lungs

Ductus arteriosus

connects pulmonary artery to aorta to bypass the lungs

Ductus venosus

connects umbilical vein to inferior vena cava to bypass the liver

What are some developmental features of First trimester

Development of heart, eyes, gonads, limbs, liver, brain

What are some developmental features of Second trimester

Tremendous growth, movement begins, face becomes human, digits elongate

What are some developmental features of Third trimester

rapid growth and brain development continue and there is transfer of antibodies to the fetus

What are the three phases of birth

cervix thins out and amniotic sac ruptures, uterine contractions coordinated by prostaglandins and ocytocin, placenta and umbilical cord are expelled

Which stage of cellular development has the greatest nuclear-to-cytoplasmic ratio?

Blastula

What layer does the notochord form from

Mesoderm

A cancer cell is removed from a patient and cultured. the cells in this culture seem to be able to replicate indefinitely with no cellular senescence. what protein is likely activated in these cells that accounts for this characteristic?

Telomerase. usually cells divide a limited amount of time because it gets too short. it’s likely that the telomerase has been activated which allows for synthesis of telomers

A child is born with an imperforate anus in which the anal canal didn’t close properly. this pathology is most likely accounted for by a failure of what

apoptosis, many places require apoptosis to remove skin like the webbing of the fingers

Following a myocardial infarction, the heart often heals by creation of a scar by fibroblasts, this is an example of what

incomplete regeneration, it does not form the original tissue