introduction to tissue - part two {module 9}

Question 1

describe what a tissue is

Answer 1

Tissues are a group of similar cells that have the same structure, working together to achieve a specific function.

Question 2

name the 4 main types of tissue

Answer 2

epithelial tissue, connective tissue, muscle tissue and nerve tissue.

Question 3

describe epithelial tissue

Answer 3

Epithelial tissue covers surfaces like the skin and cavities and tubes like the blood vessels, kidney tubules and airways. Generally speaking, epithelial tissue consists of a single layer of cells (like plant epithelial tissue), however, sometimes there might be more than one layer. The general function of epithelial cells is to provide a barrier between the outside environment and the organs it covers (protection). Epithelial cells are also specialised for secretion and absorption and protect organisms from microorganisms, injury and fluid loss. Epithelial tissue can also excrete waste products (like sweat).

Question 4

name the 6 different types of epithelial tissue

Answer 4

Simple epithelial tissue has one layer of cells.

Stratified epithelium has several layers of cells of which the bottom membrane is always attached to a basement membrane.

Squamous epithelium refers to the flat shape of the cells (think of floor tiles).

Cuboidal epithelium has cells shaped like cubes.

Columnar epithelial cells are tall or elongated (think of bricks).

Ciliated epithelium refers to the epithelial cells that contain tiny, hair-like projections.

Question 5

there are two types of squamous epithelium tissue name them

Answer 5

Simple squamous epithelium
Stratified squamous epithelium

Question 6

describe the simple squamous epithelium (where its found, its function and its general structure)

Answer 6

Simple squamous epithelium is found in capillaries and the alveoli in our lungs (the little air pockets/bubbles that make up most of the surface of our lungs). They are one cell layer thick and they are flat, thin and elliptical in shape and lie on a basement membrane.

The main function of squamous epithelial tissue is diffusion. Their structure allows for the easy movement of substances across the cells.

Question 7

describe the stratified squamous epithelium (where its found, its function and its general structure)

Answer 7

Stratified squamous epithelium is found on the skin. It consists of many layers and the cells are thin and flat. Its main function is as a protective covering.

Question 8

describe the cuboidal epithelium

Answer 8

Cuboidal epithelium has closely packed, cube-shaped cells that line the kidney tubules and some glands. It may occasionally have microvilli (small finger-like projections/ little hairs) on its surface to aid with absorption. Cuboidal epithelium cells are responsible for the absorption and secretion of substances and their main function is protection against bacteria and the wearing away of certain organs by lining various structures.

Question 9

describe the columnar epithelium

Answer 9

Columnar epithelial tissue contains elongated and large cells that line the stomach, intestines (digestive tract) and reproductive organs. Their nuclei are located at the base of the cell and the cells are connected by junctions that enable them to receive their nutrients from the basement membrane.

The main function of columnar epithelial cells is protection. They protect against bacterial infection and protect the surfaces from damage (through mucus secretion)

Question 10

define muscle tissue

Answer 10

Muscle tissue is a specialised tissue that allows the body and some of its organs to move. The cells can therefore shorten and lengthen to create movement

Question 11

muscle tissue can be divided into three types
name them

Answer 11

Skeletal - attached to our bones.
Smooth - found in the walls of the digestive tract, bladder, arteries and other internal organs.
Cardiac tissue - found in the walls of our hearts.

Question 12

define skeletal muscle

Answer 12

Skeletal muscle consists of regularly arranged bundles of long muscle cells called muscle fibres. The muscle cells lie parallel to each other. Skeletal muscle is a voluntary muscle, which means that we can consciously control it.

Inside the fibres are smaller fibres, which have light and dark bands that give the muscle its striated or striped appearance. They are also anchored to the bones by tendons.

Muscle tissue is responsible for movement in the body and the cells have many mitochondria in them as muscles require a lot of energy to function

Question 13

define smooth muscle

Answer 13

Smooth muscle cells are non-striated with tapered ends. They are spindle-shaped with a single nucleus. When the cells contract, the nuclei appear to twist in a corkscrew shape. Smooth muscle is involuntary and therefore can be found within the walls of blood vessels and in the digestive system, urinary tract and trachea.

Smooth muscle tissue is responsible for rhythmic contractions called peristalsis. It is required to move food down the alimentary canal (your food pipe) and for the dilation and contraction of blood vessels (to control blood pressure). Smooth muscle fibres can remain contracted for a longer time and can contract slower than skeletal muscle. The muscles in the uterus contract for long periods of time during labour (before birth occurs).

Question 14

define cardiac muscle

Answer 14

Cardiac muscle looks very similar to skeletal muscle, however, it has branched cells. The muscle connects at branching and irregular angles and is connected by discs. The connected branches aid with the coordinated contractions of the heart. The discs between the cells carry messages to contract from cell to cell. Cardiac muscle is involuntary (which is great for us because then we do not have to worry about our hearts beating) and is also striated in appearance.

Question 15

where can we find nerve tissue?

Answer 15

central nervous system (CNS) and peripheral nervous system (PNS).

Question 16

function of nerve tissue?

Answer 16

serves the important function of sending messages

Question 17

describe nerve tissue

Answer 17

Nerve tissue contains nerve cells or neurons. Neurons have a cell body, containing a nucleus, and long outgrowths that are called processes. The function of the processes is to conduct nerve impulses. Processes that conduct impulses towards the cell body are called dendrites, while processes that conduct impulses away from the cell body are called axons.

Axons are surrounded by a myelin sheath. The sheath’s main function is to insulate the nerve fibers and it also increases the speed of the impulses transmitted by the cell.

Question 18

what are the three types of neurons?

Answer 18

Sensory neurons
Interneurons
Motor neurons

Question 19

describe sensory neurons

Answer 19

Sensory neurons are activated by touch, light, temperature, pressure and sound etc. They are activated by our senses and are responsible for sending information about the environment, called stimuli, to the central nervous system. These neurons carry impulses or electrical signals from a receptor to the CNS.

Question 20

describe interneurons

Answer 20

Interneurons are short in comparison to the motor and sensory neurons. They act as connectors, connecting sensory and motor neurons. Impulses travel from the cell body along the short axon to the dendrites.

Question 21

describe motor neurons

Answer 21

Motor neurons cause movement, the muscle contraction. They carry impulses from the central nervous system to muscles or glands. However, more than just movement, they can also cause the secretion of substances by glands. The motor neurons cause their response by releasing neurotransmitters (chemical messengers).

Question 22

define connective tissue

Answer 22

Connective tissue is the tissue that connects. It plays an important role in supporting, connecting or separating different types of tissues and organs. Connective tissue is made up of cells, fibres like collagen and a matrix. The cells are scattered in a matrix and the nature of the matrix makes the tissue either soft or hard. The type of intercellular matrix determines the type of connective tissue.

Question 23

name the 5 kinds of connective tissue

Answer 23

blood
bone
cartilage
fibrous connective tissue
loose connective tissue

Question 24

define loose connective tissue

Answer 24

Loose connective tissue, or areolar tissue, is found in blood vessels and nerves. It is made up of collagen fibres, elastic fibres and cells attached together in a jelly-like matrix.

Collagen gives it its strength and elastic fibres allow the tissue to stretch. The function of loose connective tissue is to bind the epithelium to other tissues and hold our organs in place. It also cushions and protects our organs, acting as packing material.

Question 25

define fibrous connective tissue

Answer 25

Fibrous connective tissue, or white fibrous tissue, is found in tendons, ligaments and other tough membrane sheaths that surround our organs. The collagen fibres are non-elastic and are densely packed, making them extremely strong. They also act as shock absorbers.

Question 26

define cartilage tissue

Answer 26

Cartilage can be found in the nose, joints, sternum and trachea. It is a tough and flexible connective tissue that consists of collagen fibres and cartilage cells in a rubbery matrix. Cartilage is flexible but provides structure, strength and support. It also reduces friction.

Question 27

define bone tissue

Answer 27

Bone tissue is found in bones all over the body. It forms the skeleton and contains bone cells, collagen fibres and a hard matrix. The bone cells are found in the spaces in the matrix, and they secrete minerals (like calcium phosphate) that make bones hard. The cytoplasm of the bone cells forms long processes (like arms or tentacles) that extend through the matrix and connect bone cells to each other. These processes allow for food and gases to travel from cell to cell. Bone tissue is very strong and its function is, therefore, to provide strength and support. It also synthesises red blood cells and white blood cells

Question 28

define blood as a connective tissue

Answer 28

Blood does not look or behave like the other types of connective tissue. However, because it consists of cells in a fluid matrix and originates from bone and some fibres, it is considered a specialised form of connective tissue. The matrix consists of plasma (a yellowish fluid), which is a mix of water and salts, dissolved proteins, carbohydrates and fats. The cells are red blood cells, white blood cells and platelets.

Question 29

define red blood cells

Answer 29

Red blood cells are also called erythrocytes and are synthesised in the red bone marrow. They do not have a nucleus and are biconcave (bi = 2, concave = are dented inwards towards the centre. So they are dented inwards on both sides) in shape. This makes them quite flexible, allowing them to squeeze through narrow spaces in capillaries. It also increases the surface area-to-volume ratio, allowing them to absorb and release gases faster. Red blood cells only live for about 120 days, which means that every four months you have new blood in you

Question 30

describe the importance of the role of erythrocytes within blood

Answer 30

Erythrocytes contain a protein called haemoglobin, which contains a pigment (haeme) that has iron at its centre. The iron combines with oxygen, allowing the red blood cells to transport oxygen around the body. The haemoglobin releases oxygen as required and then picks up carbon dioxide (the waste product), taking it to the lungs so we can breathe it out. Red blood cells, therefore, transport oxygen from the lungs to the rest of the body tissue and return carbon dioxide from the body to the lungs.

Question 31

define white blood cells

Answer 31

White blood cells are also known as leukocytes and are made in the yellow bone marrow and lymph nodes. White blood cells have one or more nuclei (unlike red blood cells, which do not have any) and are larger than red blood cells. They are also irregular in shape. There are several different types of white blood cells and their main function is protection against disease.

Question 32

define platelets

Answer 32

Platelets are known as thrombocytes and are synthesised in the bone marrow. They are fragments of bone marrow cells. They do not contain nuclei and assist the blood with clotting (an awesome mechanism to prevent excessive bleeding and help us to heal).

Question 33

define plasma (in blood)

Answer 33

Plasma is the pale yellowish fluid that blood cells float in. It makes up about 55% of the total volume of blood. Plasma contains dissolved hormones, urea, proteins and carbon dioxide. The main function of plasma is to transport nutrients, cells and metabolic waste products. It also maintains blood volume.