Embryology

McKinley and O’Laughlin

Chapter 3

Introduction

All of the bodies cells arise from the zygote (fertilized egg).

We get our ~100 trillion cells from Mitosis, the production of 2 genetically identical daughter cells from 1 parental cell.

Introduction

What is the process which results in these cells specializing? Differentiation

Introduction

What is the 38-week period of development in the female reproductive system? Prenatal period

A 40 week gestation period is measured from the woman's last period, not ovulation.

Introduction

What is the study of development during this period (prenatal development)? Embryology

Introduction

What is the biological specialty that studies anatomical and physiological changes from the conception of a new individual to that individuals death? Developmental Biology

Introduction

What are the 3 periods of development from the moment of conception to birth? Pre-embryonic period Embryonic period Fetal period

Gametogenesis

What are haploid cells which are capable of producing a new diploid individual? Gametes

Gametogenesis

What are diploid cells which are distinguished from the gametes? Somatic cells

Gametogenesis

What is the distinguishing characteristic of human diploid cells? Carry 23 pairs of chromosomes

We aren’t the only species with 23 pairs, but our closest relatives have 24 pairs.

Gametogenesis

What is the distinguishing characteristic of human haploid cells? Carry 23 chromosomes

1 member of each pair Crossing over makes each chromosome different

than those receive from parents

Gametogenesis

What type of cell division produces haploid cells? Meiosis

Gametogenesis

Mitosis 2, diploid daughter

cells

Meiosis 4, haploid daughter

cells Crossing over:

Exchange of DNA between homologues

How do these 2 types of cell division (Mitosis and Meiosis) differ?

Meiosis I

Gametogenesis

Where in the body does reduction division occur? Gonads

Gametogenesis

Why is reduction division so important?

Pre-embryonic Period

What is the fertilized egg? Zygote

Pre-embryonic Period

What period of development ranges from the moment of conception until the completion of implantation into the uterine wall? Pre-embryonic

Pre-embryonic Period

What process restores the diploid number of chromosomes, determines the sex of an individual, and initiates cleavage? Fertilization

Pre-embryonic Period

Where does this process usually take place? Uterine tube (Ampulla)

Pre-embryonic Period

What series of synchronized mitotic divisions results in an increase in the number of cells? Cleavage

Pre-embryonic Period

What is the compacted 16-cell stage of development? Morula

Pre-embryonic Period

In what stage do the products of conception enter the uterus? Morula

Pre-embryonic Period

What stage of development occurs as fluids enter the products of conception (Morula at this point)? Blastocyst

Pre-embryonic Period

What are the two distinct components of this fluid-filled sphere? Which becomes the embryo? Trophoblast: becomes the chorion Embryoblast: becomes the embryo

Pre-embryonic Period

What is the process by which this sphere burrows into and embeds within the endometrium? Implantation

Pre-embryonic Period

When does the process (Implantation) begin? ~7 days after fertilization

Pre-embryonic Period

The inner cell mass (embryoblast) divides into two cell layers that form a flat disc. What is the anatomical term for this disc? Bilaminar germinal disc (blastodisc)

Pre-embryonic Period

What is the collective term for the membranes formed to mediate the exchange between the uterus and the embryo? Extraembryonic membranes

Pre-embryonic Period

Which membrane forms first and is involved in the formation of blood cells and blood vessels? Yolk sac

Pre-embryonic Period

Which membrane forms a fluid filled sac immediately around the embryo? Amnion

Pre-embryonic Period

Which membrane is outermost and eventually forms the placenta? Chorion

Pre-embryonic Period

What is the organ of exchange between the mother and the embryo? Placenta

Pre-embryonic Period

What 2 layers of tissue contribute to its formation? Fetal: Chorion Maternal: Endometrium

Pre-embryonic Period

What structure initially connects the embryo to the organ of exchange? Connecting stalk

Pre-embryonic Period

What does this initial structure develop into? Umbilical cord

Pre-embryonic Period

What stalk-like structures form from the chorion? Chorionic villi

Pre-embryonic Period

In this organ of exchange (the placenta) do the mother’s blood and the embryo’s blood mix? No

Pre-embryonic Period

What is the common name for this organ of exchange (the placenta)? Afterbirth

http://www-medlib.med.utah.edu/WebPath/PLACHTML/PLAC032.html

Embryonic Period

What process results in the formation of three primary germ layers? Gastrulation

Embryonic Period

What are the three primary germ layers? Ectoderm Mesoderm Endoderm

Embryonic Period

When does the blastocyst become an embryo? During gastrulation (after implantation) 3rd week

Embryonic Period

What type of folding results in the formation of the head and buttocks? Cephalocaudal folding

Embryonic Period

What type of folding results in the formation of the torso? Transverse folding

Embryonic Period

What structures form from the ectoderm? Nervous system Epidermis

Embryonic Period

What inductive action transforms a portion of the ectoderm into a hollow tube which develops into the nervous system? Neurulation

Embryonic Period

What structures form from the mesoderm? Muscle Connective tissue Urinary system Reproductive system Cardiovascular system Lining of body cavities

Embryonic Period

What structures form from the endoderm? Linings of

Digestive tract Respiratory tract Urinary tract

Thyroid, parathyroids, thymus Liver, gallbladder, pancreas

Embryonic Period

What is the process by which organs develop? Organogenesis

Embryonic Period

What are substances that may cause birth defects? Teratogens

Fetal Period

During what time period does the fetal period occur? Week 9 (3rd month) to birth