The Four Fundamentals: An Explanation of Body Tissue Types

Four Tissue Types

The word “tissue” describes a large mass of similar cells that work together to form a specific function. According to the book, “Anatomy and Physiology,” tissues serve various purposes, depending on where they are located in our bodies. The human body contains four types of tissue: epithelial tissue, connective tissue, muscle tissue and nervous tissue.

The epithelial tissue covers outside surfaces (such as skin), lines internal cavities (like the gastrointestinal tract) and creates certain glands (salivary and mammary glands). The primary functions of epithelial tissue are protection, secretion, absorption and reporting sensation of stimuli. In the embryonic stage, epithelial tissues are present in ectoderm, mesoderm, and endoderm germ layers.

Connective tissues, in essence, hold our body together. They are used for binding/supporting, insulation, storing extra energy, protection and moving substances throughout the body. Connective tissues include bones, ligaments, tendons, cartilage, and fat.

Muscle tissue responds easily to stimuli. Above all, muscle tissue helps us with movement (mostly through contractions). Muscle tissue is broken down into skeletal muscle, smooth muscle, and cardiac muscle. Skeletal muscles are voluntary and help us move limbs, make facial expressions and more. Cardiac muscles pump the blood in and out of our heart and are involuntary. Smooth muscle tissue works in areas like our intestine and also functions involuntarily.

Nervous tissue is referred to as “excitable” and contains neurons and neuroglia. Nervous tissue exists in our spinal cord and brain and assists with communication and integration. While the neurons transmit pulses, the neuroglia surround and support the neurons.

Anatomical Language

There is a mass amount of jargon used in the medical field to describe certain parts of the body. Seer.cancer.gov does a thorough job of explaining how these phrases are used to give reference and identify locations. The most common methods of mapping out the human body are body planes, regions, cavities, and directional terms.

Directional terms are used for describing areas of the body in relation to other parts. Superior or cranial refers to the area towards the head and upper part of the body. On the other hand, inferior or caudal is used to represent moving towards the lower half of the body. Anterior or ventral describes the front of the body while posterior or dorsal refers to the back. Medial denotes something towards the middle of the body and lateral, the opposite, means to move away from the middle. The directional term “proximal” is used to refer to the origin location of a part. Distal means to move away from the base of a body part.

Body planes define the body as a whole, from head to toe. There are four specific body planes: the Coronal plane (frontal), the Sagittal plane (lateral), the Axial plane (transverse) and the Median plane. The Coronal plane is an invisible line that goes from ear to ear and through the length of our body. It would divide our front side from our backside (anterior and posterior). The Sagittal plane would run from the top of our head to bottom of our feet, creating separate left and right sides. The Axial plane cuts horizontally at our abdomen to isolate the top half from the bottom half. The Median plane acts the same as a Sagittal plane by creating left and right halves, however, it would only stretch half the length of our body (head to stomach/stomach to feet).

Regions are another method used to compartmentalize the body. Overall, the body is split into axial and appendicular regions. The axial portion can be considered the “trunk” of the body and the appendicular portion would include limbs and appendages. The axial portion includes the thorax, head, neck, and abdomen. In contrast, the appendicular section is smaller and includes the upper and lower extremities.

Body cavities house all of our internal organs. The two primary cavities are the ventral (front of the body) and dorsal (back of the body) cavities. The ventral cavity is bigger than the dorsal cavity and is divided into the thoracic and abdominopelvic cavities. The thoracic cavity contains organs such as the heart, lungs, blood vessels, etc. The abdominopelvic cavity houses things like the gastrointestinal tract, kidneys, and adrenal glands. The dorsal cavity is posterial and can be split into the cranial cavity (our brain) and the vertebral canal (our spinal cord).

The Benefits

The four tissue types are especially important when it comes to curing disease. Since each type of ailment occurs in different types of tissue, having an understanding of each is the only efficient way to find a cure. A basic understanding of the tissue types is mandatory when looking into complex diseases that involve neurons, connective tissue, etc. Also, a clear grasp of the tissues would make it easier to notice or discover new behavior. One major benefit I see from understanding tissues is the ability to grow new replacement organs or tissue in a lab to treat disease. Being able to appropriately define sections of the body is helpful in regards to surgery and treatment. The esoteric language is a good tactic for medical professionals to communicate in a clear way that cannot be misunderstood.