published by hodder education © 2010 helen mcguinness cells and tissues

Published by Hodder Education © 2010 Helen McGuinness

Cells and tissues


1 Objectives

By the end of this chapter you will be able to recall and understand the following knowledge:

the different levels of structural organisation in the body

the importance of homeostasis and metabolism in correct body functioning

parts of a cell’s structure and their functional significance


2 Objectives

the structure and function of the main tissue types in the body

the interrelationships between the cells and tissues and other body systems

common pathologies associated with cells and tissues.


3 Key words

atommolecule

celltissueorgan

systemhomeostasismetabolism

cell membranecytoplasm

nucleusnucleolusnuclear

membranelysosomevacuole

ribosomeGolgi body

mitochondriacentrosomecentromere

centrioleschromatiddiffusionosmosisactive

transportfiltration

cell respirationtissue fluid

meiosismitosis


4 Structural organisation of the body

The human body involves five levels of structural organisation – atoms and molecules, cells, tissues, organs and systems.

Atoms and molecules are the lowest level of organisational complexity in the body.

Cells are the smallest units that show characteristics of life.


5 Structural organisationof the body

Tissues are a group of similar cells that perform a certain function.

Organs are tissues grouped into structurally and functionally integrated units.

Systems are a group of organs that work together to perform specific functions.


6 Structure of a cell

A cell is the basic, living, structural and functional unit of the body.

The principal parts of the cell are the cell membrane and its organelles which play specific roles in cellular growth, maintenance, repair and control.

The cell membrane encloses the cell and protects its contents. It is semi-permeable and governs the exchange of nutrients and waste materials.

The nucleus controls the cell’s activities and contains the genetic information.



The cytoplasm is the substance inside the cell between the plasma membrane and the nucleus.

The ribosomes are sites of protein synthesis. The endoplasmic reticulum links the cell

membrane with the nuclear membrane and assists movement of materials out of the cell.



The Golgi body processes, sorts and delivers proteins and lipids (fats) to the plasma membrane, lysosome and secretory vesicles.

The lysosome is a round sac in the cytoplasm that contains powerful enzymes to help destroy waste and worn out cell materials.

The mitochondria are the ‘powerhouses’ of the cell.



The centrosome is a dense area of cytoplasm, containing the centrioles.

The centrioles are paired small spherical structures associated with cell division, or mitosis.

The chromatids are a pair of identical strands that are joined at the centromere and separate during cell division.

The centromere is the portion of a chromosome where the two chromatids are joined.


11 Functions of cells

Functions of cells include respiration, growth, excretion, movement, irritability and reproduction.


12 Cellular respiration

Cells function through the exchange of fluids, nutrients, chemicals and ions which are carried out by passive processes such as diffusion, osmosis and filtration, and active processes such as active transport.

Cell respiration is the controlled exchange of nutrients such as oxygen and glucose and waste such as carbon dioxide by the cell to activate the energy needed for the cell to function.


13 Cellular respiration

The fuel required by cells is provided by glucose from carbohydrate metabolism and oxygen absorbed from the respiratory system into the bloodstream.

Cells are bathed in a fluid known as tissue fluid or interstitial fluid which allows the interchange of substances between the cells and the blood, known as internal respiration.


14 The cell’s life cycle

Cell division is the process by which cells reproduce themselves.

Mitosis is cell division that results in an increase in body cells and involves division of a nucleus.

Meiosis is reproductive cell division and results in the fusion of an egg and a sperm into a zygote.


15 Introduction to tissues

A tissue is a group of similar cells that are specialised for a particular function.

The tissues of the body are classified into four main types: epithelial, connective, muscular and nervous.


16 Epithelial tissue

Epithelial tissue provides coverings and linings of many organs and vessels.

There are two categories of epithelial tissue: simple (single layer) and compound (multi-layer).

There are four different types of simple epithelium: squamous, cuboidal, columnar and ciliated.

There are two different types of compound epithelium: stratified and transitional.



Type Structure Location Function

Simple squamous

A single layer of flat, scale-like cells with a central nucleus

The cells fit closely together, rather like a pavement, producing a very smooth surface

Lines the alveoli of the lungs

Lines blood and lymphatic vessels and the heart

Allows for exchange of nutrients, wastes and gases

Simple cuboidal

Single layer of cube-like cells

Ovaries, kidney tubules, thyroid gland, pancreas and salivary glands

Secretion and absorption

Simple columnar

Single layer of tall, cylindrical column cells with nucleus situated towards base of cell

Lines the small and large intestine, stomach and gall bladder

Secretion and absorption




Simple ciliated (columnar)

A form of columnar epithelium

Single layer of rectangular cells that contain hair-like projections (cilia) from its surface

Lines the upper part of respiratory system

Also lines the uterine tubes

The beating of the cilia carries unwanted particles along with mucus out of the system

Helps propel the ova towards the uterus


19 Connective tissue

Connective tissue is the most abundant type of body tissue. It connects tissues and organs to give protection and support.

Connective tissue consists of the following different types: areolar, adipose, white fibrous, yellow elastic, lymphoid, blood, bone and cartilage.




Areolar Most widely distributed type of connective tissue in body

A loose, soft and pliable tissue containing collagen, elastin and reticular fibres

Under the skin, between muscles, supporting blood vessels and nerves and in the alimentary canal

Provides strength, elasticity, connects and supports organs

Adipose A type of areolar tissue containing fat cells (adipocytes)

Surrounds organs such as kidneys and heart

Under the skin (subcutaneous layer) between bundles of muscle fibres, in yellow bone marrow of long bones and as a padding around joints

Provides insulation, support and protection

Emergency energy reserve



Type Structure Location FunctionWhite fibrous

Strong, connecting tissue made up of mainly closely packed bundles of white, collagenous fibres, with very little matrix

Contains cells called fibrocytes between bundles

Forms tendons which attach muscle to bone, ligaments which tie bones together and as an outer protective covering for some organs such as the kidney and bladder

Provides strong attachment between different structures

Yellow elastic

Consists of branching yellow elastic fibres with fibrocytes in the spaces between the fibres

Arteries, trachea, bronchi and lungs

To allow stretching of various organs, followed by a return to original shape and size

Lymphoid Semi-solid matrix with fine branching fibres

Specialised cells called lymphocytes

In the lymph nodes, spleen, tonsils, adenoids, walls of the large intestine and glands in small intestine

Forms part of the lymphatic system whose function is to protect the body from infection




Blood Also known as liquid connective tissue, contains the blood cells erythrocytes, leucocytes and thrombocytes which float within fluid called plasma

Contained within blood vessels

Helps maintain homeostasis of the body by transporting substances throughout the body, by resisting infection and maintaining heat

Bone Hardest and most solid of all connective tissues

Tough, dense compact bones and slightly less dense cancellous bone

Bones Protects and supports other organs and soft tissues

Cartilage Much firmer tissue than other connective tissues; matrix is quite solid

See next slide on types of cartilage

See next slide on types of cartilage


23 Cartilage

Type Description Location FunctionHyaline cartilage

Most abundant cartilage found in the body

Smooth, bluish-white, glossy tissue

Contains numerous cells called chondrocytes from which cartilage is produced

Found on the surfaces of the parts of bones which form joints

Forms costal cartilage which attach ribs to sternum

Forms part of the larynx, trachea and bronchi

Provides a hard-wearing low friction surface within joints

Provides flexibility in the nose and trachea

White fibrous cartilage

Tough but slightly flexible

Composed of bundles of collagenous white fibres in a solid matrix with cells scattered among them

As pads between the vertebrae called the intervertebral discs and in the symphysis pubis which joins pubis bones together

Support and to join together or fuse certain bones

Yellow elastic fibrocartilage

Yellow elastic fibres running through solid matrix, between which chondrocytes are situated

Forming the pinna (lobe of the ear) and forming the epiglottis

Provides support and maintains shape


24 Membrane

Type Description Location Function

Mucous membrane

Lines body cavities and outer layer of organs

Lines respiratory, digestive, urinary and reproductive tracts

Lines openings to external environment and secretes viscous slippery fluid (mucus) that coats and protects underlying cells

Serous membrane

Lines body cavities not open to external environment and covers many organs

Two layers: parietal which lines the wall of body cavities and visceral which provides external covering to organs in body cavities

Pericardium of the heart

Pleural membranes in the lungs

Peritoneum lining the abdominal organs

Lines body cavities not open to external environment and secretes a thin, watery (serous) fluid that lubricates organs to reduce friction as they rub against one another and against wall of cavities

Synovial membrane

Lines joint cavities of freely movable joints

Lines spaces around certain joint cavities (shoulder, hip and knee)

Secretes synovial fluid that provides nutrition and lubrication to joints so they move without undue friction

published by hodder education © 2010 helen mcguinness cells and tissues

Documents

cells structure

cell materials

cell division

cella cell

cells activities

group of similar cells

plasma membrane

bodythe human body