Structural Organization in Animals and Levels of Body Design

Cell Organelle

Function

Nucleus

It contains the hereditary material, the DNA, and is surrounded by a nuclear envelope that separates the DNA from the rest of the cell.

Endoplasmic Reticulum

It plays a major role in the metabolism of carbohydrates, synthesis of lipids, proteins, and steroids. 

Cytoplasm

It’s a thick jelly-like substance that houses various cell organelles. Many chemical reactions take place within the cytoplasm. 

Golgi Apparatus

Its major function is the transportation of materials within the cell. 

Mitochondrion

ATP- the energy currency of the cell is produced here. 

Ribosome

Known as the protein factory of a cell, all proteins are synthesized here. 

Lysosome

It engulfs foreign bodies that enter the cell and helps in cell renewal.

DNA

Deoxyribonucleic acid- the DNA is the genetic material of the cell.

Cell Membrane

Supports and protects the cell and regulates the movement of substances in and out of the cell.  It is a porous membrane and is a wall-like structure between two cells. 

Epithelial Tissue

This type of tissue consists of tightly packed sheets of cells that cover surfaces that include the outside of the body. For example, the outside layer of the human skin. The cells are polarized which means they have a top and a bottom side. The top side faces the inside cavity or the outside which is open to the air and the outside environment whilst the bottom side faces the underlying cells. Because the cells are tightly packed, it lets them act as barriers to the movement of fluids and harmful microbes. Often the cells are joined by specialized junctions that hold them tightly together. 

Connective Tissue

This type of tissue consists of cells suspended in an extracellular matrix. The matrix is made of protein fibers like fibrin, collagen, and solid, liquid, or jelly-like substance. 

The most common type of connective tissue is the loose connective tissue which is found throughout the body and it supports blood vessels and other organs. This type of tissue also links epithelial tissue to muscles that lie underneath. 

Connective tissue is found in ligaments and tendons which connect muscles to bones and one bone to another. Special forms of connective tissue include adipose tissue- body fat, blood and cartilage. In these tissues, the extracellular matrix is liquid and is called plasma. 

Muscle Tissue

Muscle tissue allows the body to move, pump blood and move food through the digestive system.

Muscle cells contain actin and myosin proteins which allow them to contract. The three types of muscles seen are

Skeletal Muscle: Also called striated, striped muscles, and are attached to tendons. It allows us to consciously control our movement.

Cardiac Muscle: Found in the walls of the heart and are striated and striped like skeletal muscles. They cannot be controlled. The individual fibers are connected to intercalated disks which allows them to contract in sync.

Smooth Muscle: Found in the walls of blood vessels and the uterus, the digestive tract, the urinary bladder, and many internal structures. They cannot be controlled and are not striped or striated.

Nervous Tissue

This type of tissue consists of neurons and neuroglial cells and functions as processing and transmitting information. Neurons generate electrical signals called nerve impulses that allow them to convey information rapidly across long distances. Neuroglia’s act to support neuronal function.

Organ System

Organ Tissues and Structures Involved

Function

Cardiovascular

Heart, blood, blood vessels.

• Transports blood, oxygen, nutrients to all parts of the body and transports wastes away from cells. 

• Stabilizes body temperature

Lymphatic

Lymph, lymph vessels, lymph nodes

• Defends our body against diseases and infections.

• Transfers lymph between the blood and other tissues.

Digestive

Mouth, salivary glands esophagus. Stomach, liver, gallbladder, pancreas, small and large intestine.

Processes food and absorbs minerals, vitamins, nutrients, and water.

Endocrine

Pituitary, pineal, thyroid and parathyroid, adrenals, ovaries, testes, endocrine pancreas (all glands)

• Secrete various hormones which have specific functions and assist in many bodily activities. 

• ADH secreted from the adrenal glands controls the passing of urine. 

Muscular

Skeletal, smooth, and cardiac muscles.

Provides movement and support to the body as well as heat production.

Nervous

Brain, spinal cord, sensory organs- eyes, ears, skin, tongue and nose, nerves 

Collects, transfers and processes information

Integumentary

Nails, skin, hair

• Protects the body from injury and fluid loss.

• Defends the body from infectious microbes.

Reproductive

Uterus, vagina, ovaries, mammary glands, testes, vas deferens, seminal vesicles, prostate, penis, fallopian tubes.

Produces gametes and sex hormones and assists in reproduction.

Respiratory

Nose, pharynx, larynx, trachea, bronchi, lungs, diaphragm, and mouth.

Respiration

Skeletal

Bones, cartilage, tendons, joints, ligaments, tendons, and joints.

• Provides movement at joints

• Supports and protects the soft tissues of the body

• Produces blood vessels

• Acts as mineral storage

Immune

Leukocytes, thymus, adenoids, spleen, tonsils

Defend against pathogens and disease-causing agents.

Urinary

Kidneys, ureters, urinary bladder, urethra

Removes excess water from the body, as well as salts and waste products from the blood.