© 2012 Pearson Education, Inc. Organs and Organ Systems Perform Complex Functions Organs –Contain two or more tissue types joined together; perform specific.

© 2012 Pearson Education, Inc.

Organs and Organ Systems Perform Complex Functions

• Organs– Contain two or more tissue types joined

together; perform specific functions

• Organ systems– Groups of organs that perform a common

function– Examples

• Digestive system: mouth, throat, stomach, intestines, and liver

• Lymphatic system: lymph nodes, tonsils, and spleen

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Body Cavities

• Anterior cavity– Thoracic cavity

• Two pleural cavities• Pericardial cavity

– Abdominal cavity

• Posterior cavity– Cranial cavity– Spinal cavity

• Tissue membranes (serous membranes) line body cavities

© 2012 Pearson Education, Inc. Figure 4.8

Pelvic cavity

Abdominal cavity

Anterior cavity

Diaphragm separates thoracic and abdominal cavities

Pleural cavity

Pericardial cavityThoracic

cavity

Posterior cavity

Vertebral canal

Cranial cavity

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• Membranes cover the surface of the body, line body cavities, and cover organs

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Tissue Membranes

• Serous membrane: reduces friction between organs

• Mucous membrane: lubricates surface, captures debris

• Synovial membrane: lines spaces in movable joints

• Cutaneous membrane: skin

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The Skin as an Organ System

• The proper name is integumentary system

• Includes skin, hair, nails, glands

• Functions – Prevents dehydration – Protects from injury – Serves as defense against microorganisms– Regulates body temperature – Makes vitamin D – Provides sensation

© 2012 Pearson Education, Inc. Figure 4.10ReceptorsNerveSweat gland

Adipose tissue

Smooth muscle

VeinArtery

Sebaceous gland

Hypodermis

Dermis

Epidermis

Small blood vessels

Hair shaft Free nerve endings

Hair root

Hair follicle

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Skin Consists of Epidermis and Dermis

• Epidermis– Outer layer – Stratified squamous epithelial cells – No blood vessels – Two major cell types

• Specialized keratinocytes• Melanocytes

© 2012 Pearson Education, Inc. Figure 4.11

Dead cells of epidermis

Living cells of epidermis

Dermis with blood vessel

Keratinocyte containing melanin

Melanocyte containing melanin granules

Dividing keratinocyte (basal cell)

Basement membrane

Blood vessel

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Skin Consists of Epidermis and Dermis

• Dermis– Lies underneath the epidermis– Supports tissues– Fibers

• Collagen• Elastic

– Cells• Fibroblasts• Mast cells• White blood cells• Fat cells

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Accessory Structures of Dermis

• Hair – Shaft– Follicle

• Smooth muscle– Attached to hair follicle, raises hair to

upright position

• Oil glands/sebaceous glands– Secretion moistens and softens skin

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Accessory Structures of Dermis

• Sweat glands– Secrete sweat, help in temperature regulation

• Blood vessels– Supply nutrients, remove waste, assist in

temperature regulation

• Sensory nerve endings– Detect heat, cold, touch, deep pressure,

vibration

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Multicellular Organisms Must Maintain Homeostasis

• Maintenance of relative constancy of the conditions of the internal environment

• Negative feedback control system: deviations from normal are detected and counteracted

• Components of a negative feedback control system – Controlled variable– Sensor– Control center– Effector

© 2012 Pearson Education, Inc. Figure 4.12

Controlled variableControlled variable

HigherHigher

Set point Set point

Lower Lower

Effector EffectorSensor Sensor

Control center Control center

a) An increase in the controlled variable causes events that lower the controlled variable toward its set point again.

b) A decrease in the controlled variable causes events that raise the controlled variable toward its set point again.

© 2012 Pearson Education, Inc. Figure 4.12a

SensorEffector

Control center

Controlled variable

Higher

Set point

Lower

a) An increase in the controlled variable causes events that lower the controlled variable toward its set point again.

© 2012 Pearson Education, Inc. Figure 4.12b

Controlled variable

Higher

Set point

Lower

SensorEffector

Control center

b) A decrease in the controlled variable causes events that raise the controlled variable toward its set point again.

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Negative Feedback Helps Maintain Core Body Temperature

• Controlled variable: body temperature

• Sensors: temperature sensors in skin and internal organs

• Control center: hypothalamus

• Effectors– Blood vessels– Sweat glands– Skeletal muscles

© 2012 Pearson Education, Inc. Figure 4.13

Core temperature Core temperature

Higher

Set point Set point

Higher

Lower Lower

Constriction of bloodvessels in skin(saves heat)

Dilation of bloodvessels in skin(promotes heat loss)

SensorsSensors

Shivering(generates heat) Sweating

Control center(hypothalamus)

Control center(hypothalamus)

to to

toto

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Homeostasis