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Chapter 20: Animal Structures and Functions

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Animal Structures (Anatomy) and Organ Systems (Physiology)

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Structures and Functions

We have been studying unicellular systems and plants so far. Now we are going to look at how animals are put together, and how the various metabolic functions are supported by specialized cells grouped into tissues, which associate with one another to form various organs. The study of structures in animals is anatomy, and a study of functions is physiology. While we make the distinction between the two areas of study, it is really impossible to talk about one without the other.

Check out the links for histology (cell study) slides and electron micrographs of the different types of cells as you have time Just click on the cell type (e.g., Epithelial), in the table below, then explore the audio slides so that you can listen to descriptions while looking at the example tissue type.


Type Notes Types of cells Arrangements Found in


Filter layer: everything that enters or leaves the body crosses epithelial tissues

Wear out and are replaced

Squamous, columnar, cuboidal, goblet (secretes mucus), transitional

Simple, stratified, pseudo-stratified.

Epithelial membrane: lines external openings with mucous

Serous membrane: lines enclosed areas

Surfaces: skin and linings of tracts


Few cells embedded in collagen fibers scattered in matrix.

Collagen, reticular, elastic fibers

fibroblasts macrophages

chondrocytes (cartilage)

Loose: fibers running throughout the body storing fluid/salts

Dense: Collagen bundles providing support

Elastic: lung tissue

Reticular: provides support

Adipose: fat storage

Cartilage: non-vascular supportive, but elastic

Bone: Supportive skeletal tissue, vascular, inflexible

Blood, lymph: individual specialized cells suspend in plasma

Cartilage, bone, blood and lymph


Contains the proteins myosin and actin in long, thin contractile fibers called myofibrils

Fiber cells: smooth



Smooth: walls of tracts, consist of spindle-shaped fibers

Skeletal: muscle masses consisting of long (2-3 cm) fibers with multiple nuclei

Cardiac: heart muscle: networks of fibers; 1-2 nuclei per fiber cell

Stomach, arm muscle, heart


Store or transmit information, communicate at synapses; dendrites receive/axons transmit


glial cells

Nerve: muerons bound together by connective tissue

Spinal column, brain

Organ systems

For an interactive view major body systems, check out the information at Human Anatomy On-line (this will run applets on your system; there are also some neat animations, so open this link in a separate window). This site divides the body into ten systems, rather than the twelve mentioned in your text.

You should be able to fill out this table on your own!

System (Typical) Components Functions
Integumentary Skin Protective covering
Skeletal Bones Support, movement
Muscular Muscles Movement
Digestive Mouth, stomach Ingest/digest food
Circulatory (cardiovascular) Heart, blood vessels Transport materials
Respiratory Lungs Gas exchange
Urinary (excretory) Kidney, bladder Excretion
Nervous Nerves, sense organs, brain Receive and process stimuli
Endocrine Ductless glands Regulate blood chemistry, growth, development
Reproductive Testes, ovaries Kids
Lymphatic Fluids, glands Returns blood to circulatory system
Immune system Glands, blood cells Attacks invading substances


Almost all body organ systems contribute to maintaining a balance of chemical and thermal factors so that the metabolic functions of the body can be efficiently carried out. An excess of a particular hormone will trigger the organs which manufacture that chemical to stop supplying it, at least until the levels drop enough. A swing in body temperature, heart beat, or nervous response will be counteracted by some response or negative feedback in the body to return the temperature, beat rate, or response level to normal.

Animals regulate their internal temperatures to maximize metabolic processes. Ectotherms (cold-blooded animals) get their heat from their environment as well as from the exothermic metabolic processes within their bodies; their body temperatures fluctuate with their surroundings. Reptiles will bask in the sun, and many insects must utilize sun and shade areas to achieve body temperatures in acceptable ranges. Endotherms (warm-blooded animals, which includes mammals), retain a constant body temperature despite their surroundings. They need to use various mechanisms (increased movement, shivering, sweating) to control body temperature in response to heat or cold in the environment.