Question

Which one of the following contains the largest quantity of extracellular material? (a) Striated muscle (b) Areolar tissue (c) Stratified epithelium (d) Myelinated nerve fibres

Short answer

Areolar tissue (b) contains the largest quantity of extracellular material.

Step-by-step solution

Identify Characteristics of each Tissue Type

First, assess the structure and composition of each tissue type. Striated muscle has some extracellular material, mainly in the form of connective tissue surrounding muscle fibers. Areolar tissue is a type of connective tissue with a gel-like matrix, providing plenty of space for extracellular material such as collagen and elastin fibers. Stratified epithelium consists of tightly packed cells with minimal extracellular material. Myelinated nerve fibers are primarily composed of nerve cells with myelin sheaths, which do provide some extracellular spacing; however, the amount is less than areolar tissue.

Compare Extracellular Material Content

Compare the amount of extracellular material that each of these tissues typically contains. Areolar tissue, which is loose connective tissue, contains the most extracellular matrix because it serves as a filler and cushioning agent. This matrix is composed of a large amount of interstitial fluid, fibroblasts, macrophages, mast cells, as well as many fibers, which all contribute to a significant volume of extracellular material.

Determine the Tissue with the Largest Quantity of Extracellular Material

Based on the comparison, it's clear that areolar tissue has the largest quantity of extracellular material among the options provided. It is designed to hold water and salts and provides nutrients and support for the surrounding structures.

Key concepts

Areolar Tissue

Areolar tissue is commonly known as one of the most widespread types of connective tissue found in the human body. Its unique feature is a loose arrangement of its fibers, which allows for a gel-like matrix to be present. This matrix fills the space between muscle fibers, blood vessels, and nerves. Because of its composition, areolar tissue serves as a flexible but robust packing material within our body, supporting and holding other tissues in place.

Within areolar tissue, you can find numerous cells, such as fibroblasts which produce fibers, immune cells like macrophages that fight off infections, and mast cells involved in inflammatory responses. The matrix itself is rich with proteins like collagen and elastin, which contribute to the resilience and elasticity required for the tissue to withstand different kinds of stress. It's genuinely a versatile tissue, providing cushioning, nutrition, and staving off harmful microorganisms. In relation to other tissues like dense connective tissue, its large quantity of extracellular material allows it to store water and solutes, thus maintaining the necessary conditions for cell life.

Striated Muscle

When we think about striated muscle, we often think about the muscles that help us perform our daily activities. This category includes skeletal muscles that are anchored by tendons to bone and are involved in voluntary movements, and cardiac muscle found in the heart responsible for pumping blood. One distinct feature of striated muscle is its visibly striped, or striated, appearance under a microscope, which is due to the arrangement of proteins that make up the muscle fibers.

While these fibers are primarily cellular, striated muscle does contain extracellular material, primarily in the form of connective tissues called endomysium, perimysium, and epimysium. These layers not only protect and support muscle fibers but also contain blood vessels and nerves, vital for muscle function and coordination. Unlike areolar tissue, the extracellular component in striated muscle is more organized and less prominent in volume, focusing more on facilitating a prompt and coordinated muscle contraction rather than a vast matrix filler.

Extracellular Matrix

The extracellular matrix (ECM) is the non-cellular component present within all tissues and organs, providing not only essential physical scaffolding for the cellular constituents but also initiating crucial biochemical and biomechanical cues that are required for tissue morphogenesis, differentiation, and homeostasis. Composed of water, proteins, and polysaccharides, it can have various degrees of rigidity and elasticity, depending on its role within different types of tissue.

The richness of the ECM comes from its components: elastin gives it the ability to stretch, collagen provides strength and rigidity, and proteoglycans and hyaluronic acid help to retain water and resist compressive forces. Through these elements, the ECM supports the cells, separates different tissues, and plays an essential role in the transportation of nutrients and waste products. In context, areolar tissue exemplifies a tissue with an abundance of ECM, serving a myriad of functions from support to nourishment, while other types such as stratified epithelium, possess less ECM, focusing more on the protective barrier function.