Biology Sylvia S. Mader Michael Windelspecht Chapter 31 Animal Organization and Homeostasis Lecture Outline See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes. 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1

31.3 The Integumentary System Biology, 9th ed, Sylvia Mader Chapter 33 31.3 The Integumentary System Animal Organization & Homeostasis Functions of skin Covers and protects underlying body regions Regulates body temperature, and Contains sensory receptors Skin and its derivatives make up the integumentary system

The Integumentary System Biology, 9th ed, Sylvia Mader Chapter 33 The Integumentary System Animal Organization & Homeostasis Regions of the Skin Epidermis - Outer, thinner region Stratified squamous epithelium New cells are pushed outward, become keratinized, and are sloughed off Melanocytes produce melanin (pigment) UV radiation can cause mutations in the DNA of skin cells, leading to skin cancer. 3

The Integumentary System Biology, 9th ed, Sylvia Mader Chapter 33 The Integumentary System Animal Organization & Homeostasis Regions of the Skin (cont.) Dermis - Deeper and thicker than epidermis Fibrous connective tissue containing elastic and collagen fibers contains: Receptors Nerve fibers Blood vessels Subcutaneous Layer - Loose, connective tissue located below dermis

The Integumentary System Biology, 9th ed, Sylvia Mader Chapter 33 The Integumentary System Animal Organization & Homeostasis Accessory Structures of Human Skin Nails Grow from nail root and form protective covering of distal portion of fingers and toes Hair follicles Begin in the dermis and continue through the epidermis Contain oil glands (sebaceous glands) which secrete sebum Lubricates the hair within the follicle as well as the skin Sweat glands Present in all regions of the skin Begins in dermis and opens either to a hair follicle or to the surface of the skin Functions to help maintain constant body temperature

Biology, 9th ed, Sylvia Mader Chapter 33 Human Skin Anatomy Animal Organization & Homeostasis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. hair shaft sweat pore Epidermis melanocytes sensory receptor capillaries oil gland arrector pili muscle Dermis free nerve endings hair follicle hair root sweat gland artery Subcutaneous layer vein nerve adipose tissue

Biology, 9th ed, Sylvia Mader Chapter 33 The Epidermis Animal Organization & Homeostasis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. flattened and dead cells Epidermis b. Basal cell carcinoma cells undergoing keratinization stem cells and melanocytes dermal projection Dermis a. Photomicrograph of skin c. Melanoma a: © John D. Cunningham/Visuals Unlimited; b: © Ken Greer/Visuals Unlimited; c: © James Stevenson/SPL/Photo Researchers, Inc.

Biology, 9th ed, Sylvia Mader Chapter 33 31.4 Homeostasis Animal Organization & Homeostasis The organ systems of the human body contribute to homeostasis The ability of an organism to maintain a relatively constant internal environment Animals vary to the degree in which they can regulate internal variables.

Biology, 9th ed, Sylvia Mader Chapter 33 Homeostasis Animal Organization & Homeostasis The organ systems of the human body contribute to homeostasis The digestive system Takes in and digests food Provides nutrient molecules that replace used nutrients The respiratory system Adds oxygen to the blood Removes carbon dioxide The liver and the kidneys Store excess glucose as glycogen Later, glycogen is broken down to replace the glucose used The hormone insulin regulates glycogen storage The kidneys Under hormonal control as they excrete wastes and salts

Biology, 9th ed, Sylvia Mader Chapter 33 Homeostasis Animal Organization & Homeostasis Homeostatic Control Partially controlled by hormones Ultimately controlled by the nervous system Negative feedback is the primary homeostatic mechanism that keeps a variable close to a set value Sensor detects change in environment Regulatory center initiates an action to bring the conditions back to normal

Regulation of Room Temperature Using Negative Feedback Biology, 9th ed, Sylvia Mader Regulation of Room Temperature Using Negative Feedback Chapter 33 Animal Organization & Homeostasis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Control center sends data to thermostat directs furnace to turn off 68°F set point Sensor 70°F too hot furnace off negative feedback and return to normal temperature stimulus too hot Homeostasis too cold negative feedback and return to normal temperature stimulus Sensor furnace on 66°F too cold Control center directs furnace to turn on sends data to thermostat 11 68°F set point

Regulation of Body Temperature by Negative Feedback Biology, 9th ed, Sylvia Mader Chapter 33 Regulation of Body Temperature by Negative Feedback Animal Organization & Homeostasis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Control center sends data to control center 98.6°F set point directs response to stimulus Sensor Effect Blood vessels dilate; sweat glands secrete. negative feedback and return to normal temperature stimulus above normal Normal body temperature below normal negative feedback and return to normal stimulus Effect Sensor Blood vessels constrict; sweat glands are inactive. Control center directs response to stimulus sends data to control center 98.6°F set point

Biology, 9th ed, Sylvia Mader Chapter 33 Homeostasis Animal Organization & Homeostasis Positive feedback is a mechanism that brings about an ever greater change in the same direction Childbirth process Positive Feedback Does not result in equilibrium Does not occur as often as negative feedback

Biology, 9th ed, Sylvia Mader Chapter 33 Positive Feedback Animal Organization & Homeostasis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2. Signals cause pituitary gland to release the hormone oxytocin. As the level of oxytocin increases, so do uterine contractions until birth occurs. pituitary gland + + uterus 1. Due to uterine contractions, baby’s head presses on cervix, and signals are sent to brain.