Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

4. Tissues & Histology

Characteristics of Epithelial Tissue

Anatomy & Physiology

4. Tissues & Histology

Characteristics of Epithelial Tissue

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2:36 minutes

Problem 21

Textbook Question

Why are there no skin cancers that originate from stratum corneum cells?

Verified step by step guidance

Understand the structure and function of the stratum corneum: The stratum corneum is the outermost layer of the epidermis, composed of dead, flattened keratinized cells (corneocytes) that lack nuclei and organelles. These cells are non-living and serve primarily as a protective barrier.

Recognize the requirements for cancer development: Cancer arises from uncontrolled cell division and mutations in the DNA of living cells. For this to occur, cells must be metabolically active and capable of undergoing mitosis.

Analyze why stratum corneum cells cannot develop cancer: Since the cells in the stratum corneum are dead and lack nuclei, they do not contain functional DNA or the ability to divide. This makes it impossible for them to undergo the mutations and uncontrolled growth necessary for cancer formation.

Identify the layers of the skin where cancer can originate: Skin cancers typically arise from living cells in the lower layers of the epidermis, such as the stratum basale or stratum spinosum, where cells are actively dividing and metabolically active.

Conclude that the stratum corneum's role is purely protective: Its function as a barrier against environmental damage and pathogens, combined with its lack of living cells, explains why no skin cancers originate from this layer.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Stratum Corneum

The stratum corneum is the outermost layer of the epidermis, consisting of dead keratinized cells that provide a protective barrier. These cells are continuously shed and replaced, which limits their exposure to carcinogenic factors. As a result, the stratum corneum does not typically give rise to skin cancers, as the cells are not viable for long-term mutation and proliferation.

Keratinization

Keratinization is the process by which keratinocytes in the epidermis produce keratin, a fibrous protein that strengthens the skin. In the stratum corneum, keratinocytes undergo a transformation into dead cells that are rich in keratin. This process not only protects underlying tissues but also reduces the likelihood of cancerous changes, as the cells are no longer metabolically active.

Skin Cancer Origins

Skin cancers typically originate from living cells in the deeper layers of the epidermis, such as the stratum basale or stratum spinosum, where cell division and mutation can occur. These layers contain actively dividing cells that can accumulate genetic mutations leading to malignancy. In contrast, the stratum corneum's dead cells lack the capacity for division and mutation, making them incapable of developing into cancer.

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Related Practice

Textbook Question

Which of the following epithelia most easily permits diffusion?

(a) Stratified squamous

(b) Simple squamous

(d) Simple columnar

Textbook Question

What are the four essential functions of epithelial tissue?

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Textbook Question

In adults, over 90% of all cancers arise in epithelium. Such cancers are called carcinomas, or adenomas (adenocarcinomas) if they arise in glandular epithelia. In fact, cancers of the skin, lung, colon, breast, and prostate are all in these categories. Why do you think this is so?

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Textbook Question

In adults, over 90% of all cancers are either adenomas (adenocarcinomas) or carcinomas. In fact, cancers of the skin, lung, colon, breast, and prostate are all in these categories. Which one of the four basic tissue types gives rise to most cancers? Why do you think this is so?

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Multiple Choice

Most cancers develop in epithelial tissues. Which epithelial tissue characteristic makes them prone to cancer?

Together the basal lamina and the reticular lamina make up the _____________________. The basal lamina is produced by the _________________, while the reticular lamina is produced by the ____________________.

A student scratched herself accidentally. What piece of evidence would suggest the scratch went through the epithelium (outermost layers of her skin) and reached the underlying connective tissue?

The epithelial tissue in the small intestine is specialized to absorb nutrients. Why would tight junctions be important in this function?

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