Chapter 22, Problem 1P

Summary Introduction

To determine: The time during which pregnancy is referred to as the embryonic stage.

Introduction: Gestation or pregnancy is the period during which the offspring develops within a woman. There involves several developmental stages of fetus.

Explanation of Solution

A typical pregnancy lasts 40 weeks and is divided into three stages called trimester. The embryonic stage is the first stage and it lasts for about 3 to 8–10 weeks after fertilization.

Summary Introduction

To explain: The time of pregnancy during which the term fetus is used.

Introduction: In humans, pregnancy is nearly nine months long, which is divided into three trimesters. It is about 38 weeks when measured from fertilization.

Explanation of Solution

Pregnancy or gestation is the period during which one or more offspring develops within a woman. The term fetus is used after 8–10 weeks of pregnancy during which the risk of miscarriage decreases considerably.

Summary Introduction

To describe: The period during which the organogenesis occur.

Introduction: The pregnancy is the period during which an organism develops from a single-celled zygote (fertilized ovum) to a multicellular organism.

Explanation of Solution

During embryonic stage, the gastrulation process leads to the formation of the three germ-layers that give rise to the development of all the organs in the animal body by the end of 8 weeks. This process is called gastrulation.