Tissues, Organs, and Organ System

nervous tissue

A body tissue that carries electrical messages back and forth between the brain and every other part of the body.

muscle tissue

A body tissue that contracts or shortens, making body parts move. Muscle tissue is essential for keeping the body upright, allowing it to move, and even pumping blood and pushing food through the digestive tract. Muscle cells, often called muscle fibers, contain the proteins actin and myosin, which allow them to contract. There are three main types of muscle: skeletal muscle, cardiac muscle, and smooth muscle.

Tissue

A group of similar cells that perform the same function.

skeletal muscle

A muscle that is attached to the bones of the skeleton and provides the force that moves the bones. which is also called striated—striped—muscle, is what we refer to as muscle in everyday life. Skeletal muscle is attached to bones by tendons, and it allows you to consciously control your movements. For instance, the quads in your legs or biceps in your arms are skeletal muscle.

respiratory system

A system of organs, functioning in the process of gas exchange between the body and the environment, consisting especially of the nose, nasal passages, nasopharynx, larynx, trachea, bronchi, and lungs.

musclular system

Allows manipulation of the environment, locomotion, and facial expression. Maintains posture, and produces heat.

unicellular organism

An organism made up of one cell.

digestive system

Breaks down food into absorbable units that enter the blood for distribution to body cells.

Multicellular

Consisting of many cells

smooth muscle

Involuntary muscle found inside many internal organs of the body. is found in the walls of blood vessels, as well as in the walls of the digestive tract, the uterus, the urinary bladder, and various other internal structures. Smooth muscle is not striped, striated, and it's involuntary, not under conscious control. That means you don't have to think about moving food through your digestive tract!

cardiac muscle

Involuntary muscle tissue found only in the heart. is found only in the walls of the heart. Like skeletal muscle, cardiac muscle is striated, or striped. But it's not under voluntary control, so—thankfully!—you don't need to think about making your heart beat. The individual fibers are connected by structures called intercalated disks, which allow them to contract in sync.

voluntary muscle

Muscle that is under direct voluntary control of the brain and can be contracted or relaxed at will; skeletal, or striated, muscle.

skeletal system

Protects and supports body organs and provides a framework the muscles use to support movement. Made up of bones and joints

reproductive system

Reproduce offspring- produce male sex cells (sperm) and female sex cells (oocytes)

How the systems work together

The cells that make up the digestive, muscular, skeletal, reproductive, and excretory systems all need oxygen from the respiratory system to function, and the cells of the respiratory system—as well as all the other systems—need nutrients and must get rid of metabolic wastes. All the systems of the body work together to keep an organism up and running.

epithelial tissue

Tissue that covers outside of the body and lines organs and cavities. consists of tightly packed sheets of cells that cover surfaces—including the outside of the body—and line body cavities. For instance, the outer layer of your skin is an epithelial tissue, and so is the lining of your small intestine. Epithelial cells are polarized, meaning that they have a top and a bottom side. The apical, top, side of an epithelial cell faces the inside of a cavity or the outside of a structure and is usually exposed to fluid or air. The basal, bottom, side faces the underlying cells. For instance, the apical sides of intestinal cells have finger-like structures that increase surface area for absorbing nutrients.

Organs

Tissues are organized into:, group of tissues that work together to perform closely related functions.

circulatory system

Transports oxygen, waste, nutrients, hormones, heat, etc... around the body

connective tissue

consists of cells suspended in an extracellular matrix. In most cases, the matrix is made up of protein fibers like collagen and fibrin in a solid, liquid, or jellylike ground substance. Connective tissue supports and, as the name suggests, connects other tissues. Loose connective tissue, show below, is the most common type of connective tissue. It's found throughout your body, and it supports organs and blood vessels and links epithelial tissues to the muscles underneath. Dense, or fibrous, connective tissue is found in tendons and ligaments, which connect muscles to bones and bones to each other, respectively.

Extra cellular fluid

fluid outside the cell. The cells get oxygen and nutrients from this extracellular fluid and release waste products into it. Humans and other complex organisms have specialized systems that maintain the internal environment, keeping it steady and able to provide for the needs of the cells.

organ system

group of organs that work together to perform a specific function

involuntary muscle

muscle that responds automatically to brain signals but cannot be consciously controlled

excretory system

the system that removes waste from your body and controls water balance

Key Points

y points Humans—and other complex multicellular organisms—have systems of organs that work together, carrying out processes that keep us alive. The body has levels of organization that build on each other. Cells make up tissues, tissues make up organs, and organs make up organ systems. The function of an organ system depends on the integrated activity of its organs. For instance, digestive system organs cooperate to process food. The survival of the organism depends on the integrated activity of all the organ systems, often coordinated by the endocrine and nervous systems.