Ch. 28 Pregnancy and Human Development
Hoehn, Haynes, Abbott12th EditionMarieb Human Anatomy & PhysiologyISBN: 9780138242732
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Table of contents
- Ch. 1 The Human Body: An Orientation25
- Ch. 2 Chemistry Comes Alive24
- Ch. 3 Cells: The Living Units24
- Ch. 4 Tissue: The Living Fabric19
- Ch. 5 The Integumentary System12
- Ch. 6 Bones and Skeletal Tissues19
- Ch. 7 The Skeleton14
- Ch. 8 Joints7
- Ch. 9 Muscles and Muscle Tissue26
- Ch. 10 The Muscular System25
- Ch. 11 Fundamentals of the Nervous System and Nervous Tissue23
- Ch. 12 The Central Nervous System25
- Ch. 13 The Peripheral Nervous System and Reflex Activity30
- Ch. 14 The Autonomic Nervous System16
- Ch. 15 The Special Senses26
- Ch. 16 The Endocrine System26
- Ch. 17 Blood27
- Ch. 18 The Cardiovascular System: The Heart25
- Ch. 19 The Cardiovascular System: Blood Vessels27
- Ch. 20 The Lymphatic System and Lymphoid Organs and Tissues16
- Ch. 21 The Immune System: Innate and Adaptive Body Defenses27
- Ch. 22 The Respiratory System21
- Ch. 23 The Digestive System31
- Ch. 24 Nutrition, Metabolism, and Energy Balance26
- Ch. 25 The Urinary System26
- Ch. 26 Fluid, Electrolyte, and Acid-Base Balance24
- Ch. 27 The Reproductive System24
- Ch. 28 Pregnancy and Human Development25
- Ch. 29 Heredity11
Hoehn, Haynes, Abbott12th EditionMarieb Human Anatomy & PhysiologyISBN: 9780138242732Not the one you use?Change textbook
Chapter 28, Problem 15
Cleavage is an embryonic event that mainly involves mitotic divisions. How does cleavage differ from mitosis occurring during life after birth, and what are its important functions?
Verified step by step guidance1
Step 1: Understand the definition of cleavage in embryology. Cleavage refers to the series of rapid mitotic cell divisions that occur immediately after fertilization, leading to the formation of smaller cells called blastomeres without an increase in the overall size of the embryo.
Step 2: Compare cleavage to typical mitosis after birth. Unlike normal mitosis, which results in cell growth and division, cleavage divisions are characterized by rapid mitosis without cell growth, meaning the total volume of the embryo remains constant while the number of cells increases.
Step 3: Identify the key differences in cell cycle phases. During cleavage, the gap phases (G1 and G2) of the cell cycle are shortened or absent, allowing for rapid DNA replication and division, whereas in postnatal mitosis, all phases of the cell cycle occur with normal timing.
Step 4: Explain the important functions of cleavage. Cleavage partitions the large zygote cytoplasm into many smaller cells, increasing the cell number to facilitate differentiation and formation of the blastula, which is essential for subsequent embryonic development.
Step 5: Summarize the significance of cleavage. It sets the stage for morphogenesis by producing a multicellular embryo from a single fertilized egg, enabling the cells to specialize and form the various tissues and organs of the body.
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Cleavage in Embryonic Development
Cleavage refers to the rapid series of mitotic cell divisions that occur immediately after fertilization, producing smaller cells called blastomeres without increasing the overall size of the embryo. This process partitions the zygote into many cells, setting the stage for further differentiation and development.
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Differences Between Cleavage and Postnatal Mitosis
Unlike typical mitosis after birth, cleavage divisions are rapid and lack the growth phases (G1 and G2), resulting in cells that decrease in size with each division. Postnatal mitosis involves cell growth and differentiation, whereas cleavage focuses on increasing cell number without growth to prepare for embryogenesis.
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Functions of Cleavage
Cleavage serves to increase cell number quickly, enabling the formation of a multicellular embryo from a single-celled zygote. It also helps distribute cytoplasmic determinants into blastomeres, which influence cell fate, and prepares the embryo for subsequent processes like gastrulation and organogenesis.
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