HSS 2305- Unit 2

What are the two stages of prenatal development?

embryonic period and fetal period

What major events occur during the embryonic period?

organs form, fertilization, blastocyst implantation

What major events occur during the fetal period?

organs grow in size and complexity

Where does fertilization occur?

in the fallopian tube

What happens during fertilization?

egg and sperm nuclei combine to form a zygote

What is a zona pellucida?

the protective coat on a zygote

What is cleavage?

very rapid cell division

What is a morula?

solid cluster of cells that develop after cleavage

What structure develops after the morula continues to divide and undergo differentiation and cavitation?

a blastocyst

What are the two layers of a blastocyst?

inner cell mass, trophoblast

What does the inner cell mass develop into?

the embryo

What does the trophoblast develop into?

the placenta

What is the role of the trophoblast?

helps the embryo implant into the uterine lining

What happens during implantation?

blastocyst adheres to inner wall of the uterus

What is an ectopic pregnancy?

pregnancy where the embryo implants outside the uterus

What does the inner cell mass transform into during week 2?

a bilaminar pancake shaped embryonic disc

What are the two layers of the bilaminar embryonic disc?

hypoblast, epiblast

What is week 1 of the emrbyonic period?

embryonic development

What is week 2 of the embryonic period?

embyronic disc

What is week 3 of the emrbyonic period?

gastrulation

What is gastrulation?

rearranging of the cells into three germ layers

What is a germ layer?

a layer of cells that will go on to form one of our organizational tubes

What are the 3 germ layers?

endoderm, mesoderm, ectoderm

What does the endoderm become?

the epithelial lining of the GI tract, liver, lungs and pancreas

What does the mesoderm become?

skeleton, muscles, heart, blood vessels, kidneys

What does the ectoderm become?

CNS, PNS, epidermis, hair and nails

What is neurulation?

first stage in the development of the nervous system

What happens during neurulation?

ectodermal cells elongate to form a neural plate then fold over and meet at the midline to form a neural tube

What does the cranial part of the neural tube become?

the brain

What causes neural tube defects?

maternal folic acid deficiency

What are neural tube defects (NTDs)?

opening in the spinal cord or brain that does not close completely

T/F NTDs are one of the most common birth defects

true

What are the two main types of NTD?

anencephaly, spinal bifida

What is anencephaly?

NTD that occurs when the head end of the neural tube fails to close

What are major signs of anencephaly?

absent skull and cerebellum, blind deaf and unconscious, still born

What is spina bifida?

unfused and open spinal cord

What is folic acid?

a b vitamin that helps a womans body produce healthy red blood cells

What causes cleft lip?

failure of the medial nasal prominence and maxillary prominence to fuse

Why can cleft palate lead to death?

the baby is unable to suck on the nipple and eat

What is zika virus associated with?

microcephaly

What does alcohol consumption increase the risk of?

miscarriages, stillbirth, prematurity, FASD

T/F trisomy 21 increases the risk of heart and birth defects

true

What does the variable gene activity hypothesis say?

activating and inactivating genes at different times in different cells causes differentiation

T/F segmentation for drosophilias are determined early in development

true

T/F drosophilia adult structures form from each segment of the embryo

true

What is neoplasia?

process of abnormal cell growth

What is a tumor or neoplasm?

abnormal growth of cells

T/F neoplasia is always cancer

false

What is a benign tumour?

localized but potentially non harmful tumour that does not spread to other tissue

What is a malignant tumor?

a tumor that invades surrounding tissue and spreads to other tissue

What is cancer?

term that encompasses 200+ diseases that occur at different ages with different rates of growth, detection evasiveness and capacities to spread

T/F all cancer is genetic and results from damaged DNA or RNA

true

What are germ line mutations?

mutations caused by mutations of the egg or sperm

What are drivers?

cancer causing mutations in tumour suppressing genes

What are passengers?

mutations that only accompany drivers and have no known cancer causing impact

What are induced mutations?

mutations caused by exposure to chemicals, viruses and UV radiation

What is angiogenesis?

vascularization of the tumor

What suffix do benign neoplasms end in?

oma

What suffix does malignant tissue originating from epithelial tissue end in?

carcinoma

What suffix does malignant tissue originating from parenchymal tissue end in?

sarcoma

What are malignant tissue originating from hematopoietic or lymphoid tissue called?

leukemias or lymphomas

T/F cancer cells have shorter cell cycles

false

T/F cancer cells move through the cell cycle many more
times than normal cells without performing normal functions of that tissue

true

In cancer cells what allows an accumulation of genetic errors?

error-prone DNA repair missed in check points

What are cyclin dependent kinases?

enzymes that act like a gas pedal that improve passage through cell phases

What do cyclins do?

bind and activate the cyclin dependent kinases

What is differentiation?

maturation of a normal cell

What is the most immature type of cell?

blast cell

T/F cancer cells lose their differentiation and appear very similar to blast cells

true

What does a low differentiation grading number for cancer cells mean?

well differentiated and specialized cancer cells

What does a high differentiation grading number mean?

poorly differentiated and poorly specialized cancer cells

What does GX describe?

tissue that cannot be assessed

What is the role of tumor suppressor genes?

code for proteins that repress the cell cycle and promote apoptosis

What is the role of proto-oncogenes?

code for proteins that stimulate the cell cycle and promote cell growth

What is an oncogene?

a gene that has the potential to cause cancer

Most cancers are caused by mutations to which two basic classes of genes

proto-oncogenes, tumour suppressor genes

What type of chromosomal mutation is the hallmark of all leukemias and lymphomas?

translocation

What are mutator genes?

DNA repair genes that prevent genetic instability

Chromosomal deletions are associated most often with what type of tumors?

solid tumors

What is gene amplification?

increase in the number of gene copies

What are growth factors?

proteins that control cell growth, differentiation and survival

What are membrane associated G proteins?

proteins that act as on/off switches for cell surface growth factor receptors

What is loss of heterozygosity?

absence of a tumour suppressor gene

T/F when a cancer cell acquires its first mutation in a gene it becomes heterozygous for that particular gene

true

What are 5 ways loss of heterozygosity can occur?

loss of chromosome, partial deletion, unbalanced translocation, loss and reduplication, miotic recombination

What are the two models of cancer evolution?

stochastic model, cancer stem cell model

What is the stochastic model?

model where each cancer cell has the ability to proliferate and form new tumours from same tissue of origin

What is the cancer stem cell model?

most cells have limited ability to proliferate but stem cells are responsible for forming sites for growth of new tumours

Why are cancer stem cells insensitive to chemotherapy and radiation?

they do not rapidly divide

What is vascular endothelial growth factor (VEGF)?

growth of new vessels

What does VEGF cause?

angiogenesis increases causig growth and spread of malignancy

What does the time spent in the cell cycle depend on?

pH of the cell, amount of oxygen, glucose and nutrients, existing space to growth

What is the three step theory?

initiation, promotion, progression

What is the initiation step?

cancer causing agent damages DNA, DNA repair is unsuccessful, permanent mutation of the cell

What is the promotion step?

carcinogen (promoter) introduced, apoptosis inhibited, tumour expansion

When does the progression step occur?

if irreversible damage to DNA occurs in promotion

What is the progression step?

accumulation of mutations

What type of tumour forms during the promotion step?

benign

What type of tumour forms during the progression step?

malignant

What are homeotic genes?

cluster of genes that determine which adult structures will be formed by each body segment