Tissue ultrastructure is a broad category and is broken down into 6 sub categories, the ultrastructure of: the lymphatic system, blood vessels, bone, muscle, nerves and skin.
The lymphatic system is a network of vessels and lymph nodes which drain and filter excess tissue fluid and return it back into the blood via the venous circulation. The main lymph organs are the spleen and the thymus. However, the thymus is more active in the early stages of life to ensure adequate T lymphocyte development. Lymph nodes take in lymph from around the body and, as they house lots of B lymphocytes and memory cells, filter the fluid of any harmful microorganisms.
The major blood vessels of the body are broadly arteries, veins and capillaries. Arteries usually carry oxygenated blood away from the heart and veins, for the most part, carry deoxygenated blood towards the heart. The capillaries have a thin endothelium and have a large surface area since nutrient absorption happens here. The vessel walls of arteries and veins contains three layers: tunica intima, tunica media and tunica adventitia.
Bone has a variety of functions including supporting the body, protection of viscera, hematopoiesis etc. As bone is a specialized form of connective tissue it contains cells + extracellular matrix. The main cell types in bones are osteoblasts, osteoclasts and osteocytes. Osteoblasts deposit osteiod and hence help build more bone. Osteoclasts break down bone by release of H+ ions. Osteocytes are old osteoblasts which become embedded within the bone matrix
Muscle is split into another 3 categories: skeletal muscle (striated and under voluntary control), smooth muscle (non-striated and under involuntary control) and cardiac (striated muscle but is under involuntary control). More about each muscle type can be learnt on our article on the ultrastructure of muscles.
In the article on the ultrastructure of nerves you will learn more the classification of neurones and their structure. For example, some neurones can be unipolar– have one process coming off their cell body. Whereas others can be bipolar-having two processes which come off the cell body.
The skin is divided into 3 main layers: the outermost epidermis, dermis in the middle and hypodermis lying deepest.
In this section, learn more about tissue ultrastructure– the lymphatic system, blood vessels, bone, muscle, nerves and skin
