Amoeba’s are single cells, where a shumans are trillions of cells working together through processes to achieve an outcome. Thus, cells specialise in something, this is called cell specialisation. Cells are the most basic building blocks in the human body. When groups come together to form a common function we call that tissues. The word tissue mean s”woven”? The study of tissues is called histology. The word origin is the Greek word “histos” meaning tissue, and “logia” meaning science.
We needed microscopes to study the bodies tissues. Given microscopes weren’t invented until 1590 it makes it a reasonably young science.
Anton Van Leewenhook ? took mirscopes from 50 x magnification to 270 x ? He was the first to see bacteria, and muscle fibres which was why people refer to him as the father of microbiolgoy.
Later hwen we invented stains and yes it was easier to see more due to more ocntrast. ONe of the earliest dyes was “carmine” which came from crushed up ?cochineal ? insetcts. The word origin of carmine is “carmin”in french, o r “irmiz” in Arabic.
We soon learned that a powerful microscope with a compatible stain could open up knowledge in wonders of the micro world, including human tissues, and how they come together to function for living organisms.
Two or more types of tissue when working together is called an organ.
There are four primary tissue types:
nervous tissue – communicates and conrolt the body
The central and perihperal nervous sytem combine to regulate all the body functions. ? Neurons nad glial cells are the two primary types of cells i nthe nervous system. ? The neuron is made up of the cell body, also called soma ?, the denedrite which look like proturding trees , and the axons which look like long connecting legs ?. The axon is like the transmission cable.
The brain is an example of something that is mostly nervous tissues ?
The other type of cells are called glial cells.
muyscles tissues – allow the body to move
Muscles tissue can contract and are well vascularised, meaning they get good blood flow.
There are three types of muscles cells:
smooth muscle tissue – This lines the wall of your blood vessels, and most of your organs. This muscle contracts slowly and automatically, and has no stripes going across it. If you remember the muscle is smooth, and contains no striations it helps.
cardiac muscle tissue – Contrary to muscle tissue this works involuntary. The contractoin of this tissue allows blood to move through the circulatory systedm. The muscle is striped, referred to as “striations” or “striated”. This muscle has cirular light bands going around it ? The connection of cells have a branching structure ?
skeletal muscle tissue – The skeletal muscle tissue is the one that pulls on your bone to allow you to move, and works largely voluntarily. Intercalated discs link the cells together, and define their borders. This is long and straight cells with multiple nuclei, and striations, or stripes that goes around it.
The shape of each cell is related to it’s function.
epithelial tissues – The proper epithelium covers and protects the outside and inside body. The glandular epithelium forms glands and secretes hormones, and other substances. The epithelium in parts of the body is invaginated, or turned inside out, or in on itself, folded back in to form a cavity or pouch.
They don’t have a direct blood supply ?, instead they rely on the supply of blood in the supporting connective tissues.
There are three basic shapes to epithelial cells: 1. Squamous 2. Cuboidal 3. Columnar
- Squamous cells are flatish cells, that quickly absorb and diffuse substances almost like a thin membrane ? The nucleus of the cell is also flat. Squamous cells are fairly flat which makes it easy for materials like oxygen to cross to the other side. Where abroption or transportation is important such as in the air sacs of the lungs you will see these cells ?
Cells create time and energy in the body to make, so in places like the mouth and skin where we need a more readily supply of new cells than other cells the body will tend to use squamous ?
- The cuboidal cells are shaped like a cube, are similiar size in height and width. They absorb nutrients and produce secretions. Their mucleus is more ciruclar than squamous cells.
- Columnar cells are long and thick, and cuhsion under lying tissues. Thei nuclei looks eliptical, alsmost as if it’s been stretched.
Cells like the stomach lining are normally columnar or cuboidal because they need room to make secretions, and other substances.
We can then classify epithelium by layers. A simple epithelium can have one layer. Multiple layers of epithelium is called stratified. They’re stacked vertically much like laying bricks on top of each other.
Pseudo stratified is basically one layer ?, but the cells can be different shapes and sizes.
If a tissue is referred to by two names, usually the first name refers to the number of layers, and the second name the shapes of it’s cells.
The epithelial tissue is also named by the direction the cells face. The apical side ?, or upper side points towards the outside of the body, whether it is towards the outside of the body or lining an internal cavity. ?body. epitheilial cells are polar ?
The basal side, is the internal side or surface.
These cells are selectively permeable allowing for some level of absorption, filtration and excretion of substances.
There is also glandular epithelium which forms the endocrine glands. The endocrine glands secrete hormones. The exocrine glands secrete their juices into tubes or ducts, as opposed to direct into the blood like the endocrine glands. ? The thyroid as an example is an endocrine gland. Examples of exocrine gland secretions are sweat, or mother’s milk if you’re lactating.
connective tissues – prdoid euspport of the bpodies. This is the most abundant tissue. It holds us together. It helps us move, transport substances in the body, store flu9id reserve and energy, insulate, protect and supoprt us.
There’s four types of connective tissue:
- Proper connective tissue – This is the type found in your skin. Fat is a type of proper connective tissue that provides insulation, ad nd fuel storage.
- Bone connective tissue –
- Cartlidge connective tissue –
- Blood connective tissue –
The bones, tendons, and ligaments support and portect and organs, and give us the skeleton which allows us to move. COnnective tissue all develop from mesenchyme.
Connective tissue has varied levels of vacularity, or blood flow. As an example cartlidge has no blood vessels. Most connective tissue is composed os the extra cellular matrix. The extra cellular matrix has sometimes been referred to as the ” filler” substance existing cells in an organism. is mainly made of two components, ine is called the groound substance. The ground substance is a felxible material ? mostly non living ? that fills in the spaces in between cells, and protects the cells.
Some connective tissue can be hard to chew for humans when eating animals which is partly why we began cooking animal meat. It wasn’t until the advent of cooking that we were able to de nature the animal extra cellular matrix ? is full of fibres, not cells. As an example some animal skin is held on with strong fibres. Cooking it allows the skin to seperate more easily from the rest of the flesh.
The connective tissue can be divided into loose and proper.
The loose connective tissue can be areolar, reticular and adipose.
The dense connective tissue can be regular, ireegular, and elastic.
Loose connective tissue is more common than dense connective tissue in humans.
Examples of loose connective tissue includes fibroblast cells, collagen fibres, and elastic fibres ?
Areolar tissue ?.
Adipose tissues include adipocytes, nucleus, and lipid vacuole.
Some tissues have more give such as , where as dense connective tissues such as tendons have less give.
Another type of tissue is cartlage. Catilage doesn’t have any blood or nerves. There’s three types of cartilage: hyaline, elastic and fibre. Hyaline is the most common type of cartilage. It contains chondrocytes and lacunae? Hyaline cartiladge looks glassy under a microscope hence hyal
Elastic cartilage is similiar to hyaline but with more elastic fibres, but in places where more elasticness or stretchiness is needed.
Fibro cartilage has many thick layers of collagen. Chondrocyte, and collagen fibres.
Bone looks like osseous connective tissue ?
There is spongy anf compact bone tissue. Spongy bone tissue is strong and poreous. In the poeous parts it stores bone marrow.
Contary to spongcy, compact bone tissue is more dense with an osteocyte within a lacuna ?
Even the leukocytes, that is the white blood cells are considered connective tissue cells.
Glycosaminlglycans are long, linear polysaccarides consisting of repeating disaccaride uints.
Collagen are strong fibress
Elastic fibre’s are long and thin, which callows them to strecth like rubber bands.
Reticular fibres are shorter collagen fibres with a coating of glycoprotein.
Cells have a mature and immautre phase.
The word “blast” means “forming”. As an example chondroblasts are the blast cells of cartidlge (spongy tissue ?). Osteoblasts. are the blast cells of bone. Once the blasts reach a mature ? phase the blast, changes it’s suffix to “-cyte”.
Proteoglycans ar ethe primary substance in the extra ceulla matrix.
The red blood cells are called erythrocytes. Proteins dissolved in the plasma form fibre like structures. White blood cells are called leukocytes