Anatomy and physiology advice to clients Connective tissue

Connective tissue or supporting tissue The human body is held together by a range of tissues that have been traditionally called connective tissue. In each of these tissues there are specialised cells that manufacture this connective tissue. In this session we shall look at the cells which synthesise connective tissue as we investigate different types of connective tissue.

Loose connective tissue Loose connective tissue is composed of loose collagen bundles, occasional fibroblasts and adipose cells. Collagen is a special protein found in connective tissue. The fibroblast cells make the collagen bundles and they replace it when it is damaged or manufacture new tissue as the body grows. You can see the loose connective tissue under the epithelial layer in this section of gut.

Dense connective tissue Dense connective tissue lays down layers of collagen bundles in sheets. It is used when strength is required. This is a section of tendon magnified about 100 times. Tendons join muscles to bones. You can see the occasional fibroblast in this section as small blue cells and you can see the wavy nature of the collagen bundles

Fibroblasts Fibroblasts are the specialised cells that manufacture collagen. You can see here in this electron micrograph the fibroblasts that are actively synthesising collagen. Look closely and you will see long parallel collagen fibrils that have been synthesised. Look at the cell in the middle, note the nucleus and the threads of collagen being extruded from the cytoplasm of the cell. This slide has been magnified about 200,000 times.

Elastic fibres Elastic fibres are widespread throughout the body where elasticity is required. Elasticity is required when a tissue has to return to an original shape and size after changing shape. Elastic fibres are made of several proteins, one of which is elastin. These fibres spring back to the original shape after being deformed. This is a cross section of an elastic artery. These arteries can expand and contract in response to changes in blood pressure. This slide has been magnified about 1000 times and stained with a special dye to show the wavy elastic fibres.

Elastic fibres If you pinch your skin you will note that it immediately falls back into place. Elastic fibres in the dermis of the skin restore skin to its original shape very quickly. You can see these fibres as blue threads in this slide. It has been magnified about 500 times. As you get older the elastic fibres start to degrade. That’s why older people have wrinkles! Apply the pinch test to your skin and note how it springs back to shape immediately after you let go.

Reticular fibres Reticular fibres are also produced by fibroblasts and they are a different type of collagen. They form a network of fibres that support the cells. Cells have a 3D volume and some require support. This picture shows reticular fibres in a lymph node magnified about 500 times. Incidentally, reticulum means net and you can see a net of fibres in this slide

Adipose cells The cytoplasm of the adipose cell (or fat cell) contains triglycerides which is the fat that is laid down in our body. Adipose cells are cells and so must have a nucleus. The nucleus is often at the periphery of the cell and if you look carefully you can see some nuclei. Adipose cells are often supported by loose connective tissue. In the top right hand corner of this slide you can see a small blood vessel which reminds us that all cells in our body are served by a blood supply

Tendons Tendons are also composed of collagen and link muscle to bone and muscle to muscle. You can see in this slide of a tendon the crimped pattern of collagen fibres forming ribbons in the tendon. Look carefully at where a muscle joins a tendon. It actually forms little anchor sites where the tendon and muscle join. In this slide you can see muscles and tendon.

Ligaments Ligaments are also composed of collagen fibres but you can see that these fibres are separated by a matrix between the fibres. Ligaments join bones together to form a joint. In this slide you can see ligament joining two vertebrae. Look closely and you will see elastic fibres. This gives this ligament additional flexibility. In these two slides you can see ligaments in situ.

Hyaline cartilage Cartilage provides a smooth surface for joint movement and a framework for bone growth. Chondrocytes are cells that make up cartilage and secrete a collagen matrix. Hyaline cartilage is the most widespread type of cartilage. We will look at hyaline cartilage in more detail when we look at skeletal tissues. Incidentally, hyaline means “glassy” and yes, when you look at it under a microscope it does look glassy just like the slide here

Elastic cartilage Elastic cartilage is found in the ear and epiglottis. Move your ear back and forward. You can feel that it returns to its shape after moving and you can feel that it is a rigid structure without being too rigid. It’s amazing isn’t it? This type of cartilage contains both collagen and elastic fibres. This is a microscope section of an ear. You can also see skin on the right hand side, elastic cartilage, adipose cells and skeletal muscle on the left

Fibrocartilage Fibrocartilage is composed of abundant collagen bundles. It is primarily found in in vertebral discs between the vertebra of the spine It is also found in the hip joint. Hormones soften this joint in pregnancy to help the birth process In the next slide you can see vertebral disks. The fibrocartilage in these disks absorb both downwards and sideways pressure on your vertebrae

Other connective tissue Bone and blood are generally regarded as connective tissue We will deal with these tissues as separate lessons

Activity Prepare some diagrams and brief notes on each of the connective tissues covered in this session so that you can explain the nature of these tissues to clients if you are requested to do so.