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 17
Why is it that only one sperm out of the hundreds (or thousands) available enters the oocyte?
Verified step by step guidance1
Understand the process of fertilization, where many sperm cells compete to penetrate the oocyte (egg cell).
Recognize that the oocyte is surrounded by protective layers, including the zona pellucida, which only allows one sperm to bind and initiate penetration.
Learn about the acrosomal reaction, where the sperm releases enzymes to digest a path through the zona pellucida, but this reaction is triggered effectively by only one sperm at a time.
Explore the concept of the cortical reaction, which occurs immediately after one sperm fuses with the oocyte membrane, causing changes in the zona pellucida that prevent any additional sperm from entering (a process called polyspermy block).
Conclude that these mechanisms ensure that only one sperm fertilizes the oocyte, maintaining the correct number of chromosomes for normal embryonic development.
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Sperm Competition and Selection
Although many sperm reach the oocyte, only one fertilizes it due to competitive and selective mechanisms. The sperm must be the first to penetrate the protective layers of the oocyte, ensuring that only the most viable sperm achieves fertilization.
Recommended video:
6:43
Clonal Selection
Zona Pellucida and Acrosome Reaction
The zona pellucida is a glycoprotein layer surrounding the oocyte that sperm must penetrate. The acrosome reaction releases enzymes from the sperm head, allowing it to digest this layer and enter the oocyte, a process that only one sperm successfully completes.
Recommended video:
01:56Chemical Reactions
Polyspermy Prevention Mechanisms
Once a sperm enters the oocyte, the oocyte triggers changes to prevent additional sperm from entering, such as the cortical reaction that hardens the zona pellucida. This ensures only one sperm fertilizes the egg, maintaining the correct chromosome number.
Recommended video:
3:02Internal Regulation - The Myogenic Mechanism
Related Practice