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 System Major 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 System Major 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 System Major 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 System Major 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 System Major 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 System Major 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 System Major 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 System Major 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 Fertilization Eggs are fertilized OUTSIDE of the FEMALE’S BODY as opposed to INSIDE the FEMALE’S BODY

Reproductive System Major Functions - Female Produces reproductive cells called eggs or ova in the ovaries Nurtures and protects developing embryo

Reproductive System Major Functions - Male Produces reproductive cells called sperm in the testes