Course 2.2Lesson 2 of 3

Connective tissue

Connective tissue connects and supports the other tissues. Its cells are spread apart in a matrix, which may be a liquid, a jelly or a solid, and the matrix decides the kind of tissue. Blood has a liquid matrix, plasma, with red cells, white cells and platelets. Bone has a hard matrix; ligaments join bone to bone and tendons join muscle to bone; cartilage, areolar and adipose tissue complete the group.

about 25 min1 simulation2 practice questions1 Python program5 questions to check yourself

This lesson is free to read. Enroll free to keep your place and take the tests.

Lesson 2 of 3Show all lessons

Try the code and the simulations beside the lesson.

The joining tissues

Your body is not a bag of separate parts. The skin is joined to the muscle, the muscle to the bone, and the organs are held in place and supplied with food and oxygen. The tissue that does these jobs is connective tissue.

Its cells are not packed closely. They are spread apart in a matrix, which may be a liquid, a jelly or a solid. The cells make the matrix, and the matrix decides the kind of tissue and its job. In a wall, the bricks are the cells and the cement is the matrix.

Blood

Blood is a connective tissue with a liquid matrix, called plasma. It connects all the parts of the body by carrying things between them. An adult has about 5 litres of blood.

Plasma is a pale yellow liquid, about 90% water, carrying food, carbon dioxide, wastes and hormones. It is about 55% of the blood.
Red blood cells carry oxygen with haemoglobin, which has iron in it and makes blood red. A red cell has no nucleus, which leaves more room for haemoglobin, and lives about 120 days.
White blood cells fight germs. They are fewer but larger, and have a nucleus.
Platelets are small pieces of cells that help the blood clot at a cut.

A drawing of blood. Many round red blood cells, which carry oxygen, one larger white blood cell with a purple nucleus, which fights germs, and a few small platelets, which help the blood to clot, lie in a pale yellow liquid, the plasma.

You should find that a body with 5 L of blood holds about 2.75 L of plasma and 2.2 L of red cells. White cells and platelets are only about 1% of the volume, though they matter just as much.

A person without enough haemoglobin has anaemia and feels tired, because the body gets too little oxygen. Food with iron, such as green leafy vegetables, helps to prevent it.

Bone

Bone has a hard matrix of calcium and phosphorus. It forms the skeleton: it supports the body, protects organs such as the brain, and anchors the muscles. Some bones hold soft marrow, where new blood cells are made. Bone is living tissue and can repair itself.

Joining tissues

Ligament joins bone to bone. It is strong and elastic.
Tendon joins muscle to bone. It is strong, with little stretch.
Cartilage has a smooth, flexible matrix, at the ends of bones in joints, in the nose, the ear and the windpipe.

Tissue that fills the spaces

Areolar tissue is soft and loose. It fills the space between skin and muscle, supports organs and helps repair them.
Adipose tissue stores fat, below the skin and between organs. It is a store of energy, an insulator, and a cushion.

Tissue	Matrix	Main job
Blood	liquid (plasma)	carries oxygen, food and wastes; fights germs
Bone	hard	supports and protects
Ligament	tough, elastic	joins bone to bone
Tendon	tough, not elastic	joins muscle to bone
Cartilage	smooth, flexible	cushions joints, supports nose and ear
Areolar	soft, loose	fills spaces, supports organs
Adipose	soft, with fat cells	stores energy, insulates

Try it in Python

Practise with new numbers

Common mistakes

Mixing up ligament and tendon. Ligament: bone to bone. Tendon: muscle to bone.
Thinking blood is not a tissue. It is a connective tissue with a liquid matrix.
Saying the red colour comes from the plasma. It comes from haemoglobin in the red cells.
Thinking cartilage is bone. Cartilage is soft and flexible.

Remember these

Connective tissue has cells spread in a matrix: liquid in blood, hard in bone, flexible in cartilage.
Blood: plasma, red cells (oxygen), white cells (germs), platelets (clotting).
Ligament: bone to bone. Tendon: muscle to bone. Adipose tissue stores fat.