Body Systems

A Brief Overview

Levels of Organization in Living Things

• Cell– Red blood cell– Epithelial cell – Neuron

• Tissue– Epithelial tissue– Connective tissue– Nervous tissue– Muscle tissue

• Organ– Skin– Brain– Heart

• Organ System– Nervous– Integumentary– Lymphatic

• Organism

Nervous SystemMajor Functions

• Controls and coordinates the functions throughout the body by transmitting electrical signals or impulses via neurons

• Responds to internal and external stimuli in order to maintain homeostasis

Examples of Nervous Systems in Animals

• Nerve Net (individual nerve cells) - Cnidarians

• Ganglia (more centralized nerve cells) – worms, mollusks & arthropods

• Neurons• Cephalization

(concentration of nerves at the head or anterior end of organism leading to the development of a true brain)

Skeletal SystemMajor Functions

• Supports the body• Protects the

internal organs• Serves as muscle

attachment for movement

Examples of Skeletal Systems in Animals

• Hydrostatic Skeleton: fluid filled body cavity that supports the muscles found in some worms & cnidarians

• Exoskeleton: external skeleton made of chitin found in arthropods

• Endoskeleton: internal skeleton made of calcium found in echinoderms & vertebrates

Muscular SystemMajor Functions

• Works with the skeletal system to provide voluntary movement

• Provides involuntary movement such as pumping and circulating blood & moving food through the digestive system

Integumentary SystemMajor Functions

• Serves as a barrier against infection and injury

• Regulates body temperature in order to maintain homeostasis

Examples of Integumentary Systems in

Animals•Skin•Hair & Fur•Nails •sweat & oil

glands•Feathers•Scales

Circulatory SystemMajor Functions

• Transports oxygen, nutrients & hormones to all the cells throughout the body

• Fights infection• Removes metabolic

wastes• Regulates body

temperature in order to maintain homeostasis

Examples of Circulatory Systems in Animals

• Open Circulatory System: Blood is not completely contained in vessels (blood found in sinuses or open cavities) –Most Mollusks & Arthropods

• Closed Circulatory System: Blood is contained in vessels - some worms & mollusks and vertebrates

• More complex systems & hearts develop as organisms move up the evolutionary ladder

Respiratory SystemMajor Functions

• Provides oxygen for cellular respiration

• Removes excess carbon dioxide from the body

Examples of Respiratory Systems in Animals

• Must have large surfaces for diffusion

• Must be moist• Skin – worms &

mollusks• Gills – aquatic

animals• Lungs –

terrestrial animals

Digestive SystemMajor Functions

• Breaks down large molecules of food into simpler, smaller molecules to be used by the cells of the body – glucose for cellular

respiration

• Absorbs nutrients• Eliminates wastes• Food moves through

the digestive system thru a muscle action called peristalsis

Examples of Digestive Systems in Animals

Intracellular vs. Extracellular Digestion: Food digested within cells as opposed to food digested outside of the cells in

a digestive cavity or a digestive tract (more complex animals)

Excretory SystemMajor Functions

• Eliminates metabolic wastes from the body in order to maintain homeostasis

• Regulates water also to maintain homeostasis

Examples of Excretory Systems in Animals

• Flame cells (eliminates excess water from flatworms)

• Skin & Gills (aquatic organisms)

• Nephridia (annelids & mollusks

• Malpighian Tubules (arthropods such as insects & arachnids)

• Kidneys (vertebrates)

Reproductive System: General

• Most invertebrates reproduce SEXUALLY during at least part of their life cycle.

• Depending on environmental conditions, many invertebrates may also reproduce ASEXUALLY

REMEMBER… THERE ARE ADVANTAGES & DISADVANTAGES TO BOTH

External vs. Internal FertilizationEggs are fertilized OUTSIDE of the FEMALE’S BODY as

opposed to INSIDE the FEMALE’S BODY

Reproductive SystemMajor Functions - Female

• Produces reproductive cells called eggs or ova in the ovaries

• Nurtures and protects developing embryo

Reproductive SystemMajor Functions - Male

• Produces reproductive cells called sperm in the testes