CHAPTER 3 – Integumentary System

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CHAPTER 3 – Integumentary System

49 2 1 The integumentary system is made up of the skin and the subcutaneous layer that underlies it. This system makes up most of the external surface of the body. Because of its position, the integumentary system is always in direct contact with the external environment and lies between it and the internal environment of the body. Therefore, this system plays a major biological role in maintaining a person's homeostasis and thus that person's happy and healthy survival. The major functions of the integumentary system are serving as a barrier between the body and its surroundings, providing information about the external environment, regulating body temperature, starting the process of vitamin D production, and actively defending the body from harmful physical and biological factors. In addition, because it is a highly visible system, it frequently affects the social, psychological, and economic aspects of a person's life.

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Gathering information about conditions in and around the body is essential for survival. It is the first step in negative feedback and positive feedback systems that help maintain homeostasis.

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Since the integumentary system is between most cells of the body and the external environment, it can supply information about factors that might alter internal conditions of the body even before those factors have an opportunity to do so. For example, many abundant nerve cells in the integument continuously monitor the external environment and send messages to other parts of the nervous system. As a result, the person knows much about the area surrounding the body, including the location, size, shape, texture, movement, and temperature of objects and materials (e.g., clothes, furniture, water, air). Then the person can take steps to avoid or correct any threatening features, perhaps before harm is done. Information provided by nerve cells in the integumentary system can also provide pleasure that can improve the quality of life. Examples include enjoyment from physical touches (e.g., hugs, caresses) and temperatures (e.g., cool breeze, warm blanket). In later parts of this chapter, other types of cells are mentioned that monitor conditions to initiate negative feedback or helpful positive feedback activities contributing to homeostasis.

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Add new section as fifth main function of the integumentary system.

Defense

The integumentary system provides defense when components assist actively in isolating, destroying or removing a harmful agent from the body (e.g., splinter, poison ivy sap, bacteria, viruses, cancer cells). Negative feedback (e.g., healing) and helpful positive feedback (e.g., inflammation, immune reactions) are used in defense activities. Defense prevents or limits damage from the harmful agent in the integumentary system and reduces the risk of damage in other body regions from agents that may spread (e.g., toxins, infection, cancer).

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Keratinocytes produce several substances that help regulate inflammation and immune responses, which are defense activities. The stratum corneum provides a barrier against microbes; many chemicals, including water; and abrasion. Though it is always being gradually worn away at the outer surface, it is maintained by having new keratin produced at the same rate by the next generation of keratinocytes. The stratum corneum serves well as long as it remains thick enough and is not broken by cuts, tears, scrapes, or burns.

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Fig. 3.3

Erythrocytes are red blood cells (RBCs), leucocytes are white blood cells (WBCs), and thrombocytes are platelets.

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For Internet images of integumentary system abnormalities, search the Images section of http://www.google.com/ for the specific abnormality (e.g., sun damaged skin, decubitus ulcer, skin neoplasia, skin cancer).

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© Copyright 2006 - Augustine G. DiGiovanna - All rights reserved.
This material MAY be reproduced or distributed in any form or by any means, or stored in any data base or retrieval system ONLY under one of the following two conditions: (1) If no individual, group, organization, institution, company, corporation or other entity is charged for its use and only for use by instructors and students in courses where students are required to purchase the book HUMAN AGING: BIOLOGICAL PERSPECTIVES by Augustine G. DiGiovanna, The McGraw-Hill Companies, New York, 1994 or 2000; (2) If prior written permission is obtained from Augustine G. DiGiovanna.

Page	Col.	¶	CHAPTER 3 – Integumentary System

49	2	1	The integumentary system is made up of the skin and the subcutaneous layer that underlies it. This system makes up most of the external surface of the body. Because of its position, the integumentary system is always in direct contact with the external environment and lies between it and the internal environment of the body. Therefore, this system plays a major biological role in maintaining a person's homeostasis and thus that person's happy and healthy survival. The major functions of the integumentary system are serving as a barrier between the body and its surroundings, providing information about the external environment, regulating body temperature, starting the process of vitamin D production, and actively defending the body from harmful physical and biological factors. In addition, because it is a highly visible system, it frequently affects the social, psychological, and economic aspects of a person's life.
50	1	3	Gathering information about conditions in and around the body is essential for survival. It is the first step in negative feedback and positive feedback systems that help maintain homeostasis.
50	1	4	Since the integumentary system is between most cells of the body and the external environment, it can supply information about factors that might alter internal conditions of the body even before those factors have an opportunity to do so. For example, many abundant nerve cells in the integument continuously monitor the external environment and send messages to other parts of the nervous system. As a result, the person knows much about the area surrounding the body, including the location, size, shape, texture, movement, and temperature of objects and materials (e.g., clothes, furniture, water, air). Then the person can take steps to avoid or correct any threatening features, perhaps before harm is done. Information provided by nerve cells in the integumentary system can also provide pleasure that can improve the quality of life. Examples include enjoyment from physical touches (e.g., hugs, caresses) and temperatures (e.g., cool breeze, warm blanket). In later parts of this chapter, other types of cells are mentioned that monitor conditions to initiate negative feedback or helpful positive feedback activities contributing to homeostasis.
50	2	4	Add new section as fifth main function of the integumentary system. Defense The integumentary system provides *defense* when components assist actively in isolating, destroying or removing a harmful agent from the body (e.g., splinter, poison ivy sap, bacteria, viruses, cancer cells). Negative feedback (e.g., healing) and helpful positive feedback (e.g., inflammation, immune reactions) are used in defense activities. Defense prevents or limits damage from the harmful agent in the integumentary system and reduces the risk of damage in other body regions from agents that may spread (e.g., toxins, infection, cancer).
51	1	1	Keratinocytes produce several substances that help regulate inflammation and immune responses, which are defense activities. The stratum corneum provides a barrier against microbes; many chemicals, including water; and abrasion. Though it is always being gradually worn away at the outer surface, it is maintained by having new keratin produced at the same rate by the next generation of keratinocytes. The stratum corneum serves well as long as it remains thick enough and is not broken by cuts, tears, scrapes, or burns.
57	1	Fig. 3.3	Erythrocytes are red blood cells (RBCs), leucocytes are white blood cells (WBCs), and thrombocytes are platelets.
63	1	4	For Internet images of integumentary system abnormalities, search the Images section of http://www.google.com/ for the specific abnormality (e.g., sun damaged skin, decubitus ulcer, skin neoplasia, skin cancer).