The key difference between epithelium and connective tissue is that epithelium is the tissue that lines outer surfaces of organs and blood vessels as well as inner surfaces of cavities of organs while connective tissue is the tissue that separates, connects and supports various tissues and organs in an animal body.
There are four types of animal tissues as epithelium, connective tissue, muscle tissue and nervous tissue. A tissue is a group of cells that carry out a specific function. The intercellular substances link cells of the tissue physically. Tissue specialization increases the efficiency of the organism functionally. Connective tissue and epithelium work in close connection while surrounding organs and organ systems.
CONTENTS
1. Overview and Key Difference
2. What is Epithelium
3. What is Connective Tissue
4. Similarities Between Epithelium and Connective Tissue
5. Side by Side Comparison – Epithelium vs Connective Tissue in Tabular Form
6. Summary
What is Epithelium?
The epithelium is an animal tissue that lines the internal and external surfaces of an organism, especially the outer surfaces of organs and blood vessels and inner surfaces of cavities of organs. It can be arranged in a single cell layer or several layers. True epithelial tissue arises from the embryonic ectoderm, which provides epithelium for the skin, nervous system and parts of the midgut and the hindgut. Furthermore, the embryonic endoderm provides epithelium for the remainder of the alimentary canal, liver, and pancreas.
Figure 01: Epithelium
Hyaluronic acid cements the epithelial cells together. The cells can be shaped in squamous, columnar and cuboidal. The bottom layer of the epithelium rests on a basement membrane composed of collagenous fibres and it is avascular. So, the epithelium depends on the underlying connective tissue for nutrition, communication and oxygen. There are two types of epithelial tissues as simple epithelium and compound epithelium. Simple epithelium has a single cell layer and it mostly lines the internal surfaces, while compound epithelium has multiple cell layers and it lines the external surfaces and distensible internal surfaces.
What is Connective Tissue?
Connective tissue is the main supporting tissue of the body. It includes the skeletal tissue, loose connective tissue, fibrous connective tissue and haemopoietic tissue. Connective tissue connects other tissues together. Furthermore, connective tissue form sheaths around the organs of the body and separate them in order to prevent the interferences of their works. Connective tissue is a composite tissue made up of different kinds of cells of the embryonic mesodermal origin. It mainly consists of fibre (non-living products of cells) and a semi-fluid intercellular matrix consisting of hyaluronic acid, chondroitin, chondroitin sulphate and keratin sulphate.
Figure 02: Connective Tissue
Connective tissues are present all over the body. They carry out different functions including the protection through macrophages and mast cells. An extensive vascular network is often present in the connective tissue. Hence, it supplies nutrients and oxygen to other tissues as well. It also provides insulation of body heat by the function of the adipose tissue. Moreover, connective tissue provides a supporting network to the bones and muscles of skeletal tissue. Being a haemopoietic tissue, it produces blood and lymph as well.
What are the Similarities Between Epithelium and Connective Tissue?
- Epithelium and connective tissue are two of the four types of animal tissues.
- Both connective and epithelial tissues mainly have a structural function.
- They both consist of a strong fibrous component.
- These two tissue types have the common function of protection from foreign bodies and toxins, as well as mechanical damage.
- These two types of tissues together form the majority of organs and systems that make the animal body.
What is the Difference Between Epithelium and Connective Tissue?
Epithelium is the animal tissue that lines external and internal surfaces of organs and cavities. In contrast, connective tissue is an animal tissue that supports, connects and separates tissues and organs of the body. So, this is the key difference between epithelium and connective tissue. Furthermore, connective tissue forms the subtypes of skeletal tissue, forming strong bones and muscle, as well as fluid tissue such as blood and lymph. But epithelium rarely shows a variation in tissue structure apart from the number of layers of cells. This is another difference between epithelium and connective tissue.
The connective tissue has a rich network of nerves and blood capillaries, unlike the epithelium. This is an important difference between epithelium and connective tissue. The epithelial cells are always arranged in an orderly fashion on the basement membrane, while the connective tissue does not have a basement membrane.
The below infographic summarizes the difference between epithelium and connective tissue.
Summary – Epithelium vs Connective Tissue
Epithelium and connective tissue are two animal tissues. Epithelium protects the body by lining outer surfaces of organs and blood vessels and inner surfaces of cavities of organs while connective tissue separates, connects and supports various tissues and organs in the animal body. Thus, this is the key difference between epithelium and connective tissue. Both tissues are important and they work together. Epithelial cells rest on a basement membrane while connective tissue cells do not rest on a basement membrane. However, connective tissue has a good blood and nerve supply while epithelium does not.
Reference:
1. “Epithelium.” Wikipedia, Wikimedia Foundation, 18 Aug. 2019, Available here.
2. Boundless. “Boundless Anatomy and Physiology.” Lumen, Available here.
Image Courtesy:
1. “Epithelial Tissues: Stratified Squamous Epithelium” By Berkshire Community College Bioscience Image Library (Public Domain) via Flickr
2. “Connective Tissue: White Fibrous Connective” By Berkshire Community College Bioscience Image Library (Public Domain) via Flickr