[Biology Class Notes] on Adipose Tissue Pdf

Adipose tissue is a complex, essential, and highly active metabolic and endocrine organ. It is a source of several hormones, including leptin, estrogen and resistin. Adipose tissue is composed primarily of adipocytes or fat cells. These comprise lipid storage droplets, which contain triacylglycerol and vary in size depending on the amount of stored fat. The following article covers various aspects of adipose tissue, such as its types, structure, location, and function. So, let us start with what the adipose tissue in the coming section:

 

What is Adipose Tissue?

The group of cells which have a similar structure and function that acts together to perform the desired function are called tissues. There are four different kinds of tissues in animals, they are: 

1. Connective tissue

2. Muscular tissue

3. Epithelial tissue

4. Nervous tissue

The connective tissue has two different subclasses, they are loose connective tissue and dense connective tissue. These subclasses can further be divided as follows:

 

1. Loose Connective Tissue: 

• Areolar connective tissue

• Adipose connective tissue 

• Reticular connective tissue

 

2. Dense Connective Tissue:

 

Adipose Connective Tissue

The specialized type of connective tissue consists of fat or lipid cells called adipocytes. In a healthy person, 20 to 25% of total body weight is composed of fat tissue. The adipose tissue’s main function is to store energy in the form of fat. Adipose tissue comprises multiple nerve cells and blood vessels in addition to fat cells, storing and releasing energy to fuel the body as well as releasing critical hormones essential to the body’s needs.

 

Types of Adipose Tissue

1. Based on the location they are present, it is divided into two types, they are visceral fat and parietal fat.

2. Based on the structure, it can be divided into, white adipose tissue and brown adipose tissue.

 

Adipose Tissue Function

Along with the storage of fat cells, these cells help to perform different functions such as:

• It is a metabolic organ that helps in the regulation of homeostasis.

• Thermal isolation.

• Production of a great number of bioactive factors.

• Acts as an endocrine gland that is responsible for the production of hormones.

• Helps in cushioning the organs.

 

Adipose Tissue Location and Structure

The tissue that stores fat in our body is adipose tissue, this fat is distributed all over in two ways, they are:

1. Parietal fat is also called subcutaneous fat that is found present under the skin.

2. Visceral fat is found surrounding the internal organs such as eyeballs or kidneys.

 

The adipose tissue consists of cells and an extracellular matrix. These cells are the most abundant and structural elements that are distributed throughout the small amount of the cellular matrix. The main type of cells that are found are adipocytes. Including this there are other different kinds of cells, are fibroblasts, preadipocytes, capillary endothelial cells, macrophages, and stem cells. These cells are commonly called non-adipocyte cells. The non-adipocytes combine to form a stromal vascular fraction. The adipocytes function is to support and protect the adipose tissue.

 

The adipocytes and the stromal cells help in the production of the extracellular matrix. The matrix consists of reticular fibers that are connected as a fine network that helps to hold and place the cells. The adipose tissue has a rich supply of blood vessels and unmyelinated nerve fibers.

 

Adipocytes

Adipocytes are the building blocks of adipose tissue. They are also known as fat cells or adipose cells. The adipocytes are divided into two types depending on the distribution of two types of adipose tissue.

• White Adipocytes: It consists of the main cells of the white adipose tissue. The shape can vary from spherical to oval or polyhedral. It consists of a single lipid droplet that pushes the nucleus to the peripheral side of the cell. The cytoplasm is present around the lipid droplet and contains fewer mitochondria. 

• Brown Adipocytes: It consists of chief cells of brown adipose tissue. They are very small in size and consist of multiple lipid droplets. These droplets surround the nucleus that is present in the centre. It has numerous mitochondria that are found dispersed among the droplets which give them a brown colour. Golgi apparatus, a small number of ribosomes, and endoplasmic reticulum can also be found in the cytoplasm. 

• Beige Adipocytes: It is found dispersed in the white fat tissue. A small portion of it can also be found in visceral fat. 

Adipose can perform different functions depending on the location it is present. 

1. The abdominal fat has a different kind of metabolic function compared to all other fat in the body, and
   it can also influence the inducing insulin resistance. 

2. Parietal fat helps in thermoregulation.

3. Visceral fat provides cushion-like support to the internal organs by protecting them from mechanical injuries.

 

The adipose tissue is very crucial for health, it is not only important for the storage of fat cells it also contains plenty of nerve cells and blood vessels that help in the storage and releasing of the energy to the body. The excess of fat content in the body can lead to medical conditions such as obesity and the loss of healthy body fat can lead to a condition called lipodystrophies.

 

Important facts about Adipose Tissues

Adipose tissue is a special and different type of connective tissue, mainly composed of fat cells called adipocytes. Adipocytes are classified into three types: white adipocytes, brown adipocytes, and beige adipocytes. Their structure, location, and function are different. Therefore, adipose tissue can be divided into white adipose tissue mainly composed of white and beige fat cells and brown adipose tissue composed of brown fat cells. White adipose tissue is the main type of fat in the human body. It can be found under the skin (subcutaneous fat), around the internal organs (visceral fat) and in the central cavity of the bones (marrowfat), and can cushion various parts of the body. Its main work is to act as an energy store, but it also protects the body from extreme temperatures, provides a buffer for vital organs, and secretes hormones and biological factors. Brown adipose tissue mainly exists in the fetus and infancy. It is mostly seen in the upper back, above the clavicles, in the mediastinum, and surrounding the vertebrae. Brown adipose tissue’s major function is to generate heat through non-shivering thermogenesis, which is particularly important in preventing hypothermia in newborns.