Living Processes of Multicellular Organisms

2.3

Living Processes in Multicellular Organisms

Introduction

There are various types of cells in multicellular organisms which are different in size, shape and arrangement
The cell structure correlates to its function, and each type of cell is specialised to carry out a specific function

Types of Specialised Cells in Humans

Muscle Cell

Arranged as multinuclear striated fibres
Contract and relax to generate movement

Nerve Cell

Long and thin in shape
Functions in sending nerve impulses

White Blood Cell

Can change shape
Functions in destroying pathogens

Red Blood Cell

Does not contain a nucleus
Shaped as a biconcave disc
Functions to optimise transportation of oxygen

Epithelial Cell

Thin and flat cells
Coats the surface of organs such as the digestive tract

Sperm Cell

Has a long tail to enable it to swim towards the ovum in the Fallopian tube
The head carries a set of chromosomes from the male

Types of Specialised Cells in Plants

Sieve Tube Element

Long cylindrical tubes arranged from end to end
Transports organic materials from leaves to storage organs such as fruits

Xylem Vessel

Long, continuous hollow tube
Functions in transporting water and mineral salts from the roots to the other parts of the plant

Palisade Mesophyll Cell

Consists of long cylindrical cells, arranged vertically and close to each other
Contains high chlorophyll density
This arrangement allows maximum absorption of sunlight for photosynthesis

Spongy Mesophyll Cell

Cells are loosely arranged with lots of air space in between
Large air space allows exchange of gas from the inside of the leaves to the palisade mesophyll cells

Guard Cell

Modified lower epidermal cells with the thicker cell wall on the inner side
Controls the opening and closing of the stoma. Stoma is the opening that allows the exchange of oxygen and carbon dioxide

Root Hair Cell

Has a long projection which adds surface area for the absorption of water and mineral salts

Cell Organisation in Human

Tissues are a group of cells that have the same structure and function and are arranged together to carry out a specific function
In organisms, tissues can be classified into four different types which are epithelial tissue, muscle tissue, nerve tissue and connective tissue

Types of Tissues in Human

Epithelial Tissue

Epithelial tissue covers the outer surface (skin) and hollow surfaces in the body (digestive tract and respiratory tract)
The epithelial tissue structure is adapted based on its function
For example, the epithelial tissue on the skin protects against infections, injuries, chemicals and dehydration.
Epithelial tissue covers the surface of the mouth, oesophagus, covers the surface of lungs, body cavities, blood vessels, covers the surface of the trachea, bronchus, lines tubules, glands, kidney ducts and small intestine
Epithelial tissues that coat the trachea have projections like hair, known as cilia (singular: cilium)

Muscle Tissue

There are three types of muscle tissue: smooth muscle (found in the digestive tract, blood vessel, urinary tract and reproductive tract), skeletal muscle (found in legs and hands) and cardiac muscle (found in the heart wall)
Contraction and relaxation of smooth muscle enable involuntary activities such as peristalsis along the digestive tract
Skeletal muscle is involved in controlled movement
Skeletal muscles contract and relax to generate movement in bones and limbs
Cardiac muscle builds walls of the heart that contract to pump blood to the whole body
Cardiac muscle contraction is involuntary

Nerve Tissue

Nerve tissue is made of neuron or nerve cells
Each neuron consists of a cell body and nerve fibre called dendrite and axon
Nerve tissues can detect stimuli and then send information in the form of an electrical signal (nerve impulses) to the muscles or glands
Nerve tissue regulates and controls body activity

Connective Tissue

The connective tissue consists of various types of tissues and fibres
This tissue is distributed all over the body and has many functions
One of its functions is to link the organs
Loose connective tissue: it links the epithelial tissue to the tissue below it, and fixes the organs in their positions
Blood tissue: blood plays a functional role in regulation, transportation and protection
Fibrous connective tissue: these tissues form tendons (connect bones and muscles) and ligaments (connect bones to bones)
Bone: bone forms the body frame and protects the internal organs
Adipose tissue: connective tissues that keep fat under the skin dermis and the surface of all main organ
Cartilage: cartilage encloses bone tips to prevent the bone from wearing out

Tissue Organisation in Plants

Parenchyma Tissue

Functions to store starch, protein and water
This tissue can also carry out photosynthesis

Collenchyma Tissue

Functions in giving support to young, non-woody stems (herbaceous plants)

Sclerenchyma Tissue

Functions in providing support and mechanical strength to all mature parts of the plant

Vascular Tissue

Vascular tissues are made up of xylem tissue and phloem tissue

Xylem Tissue

The xylem functions in transporting water and mineral salts from the roots to other parts of the plant
Lignin of xylem tissue wall provides support and mechanical strength to the plants

Phloem Tissue

The phloem functions in transporting organic matters such as sucrose from the leaves to all parts of the plant

Density of Certain Cell Component and Specialised Cell Functions

Mitochondrion

Sperm cell: requires a lot of energy to swim towards the uterus and Fallopian tube to fertilise the secondary oocytes
Muscle cell: requires a lot of energy to contract and relax to enable movement and flight
Plant meristem cell: requires a lot of energy to carry out active cell division process to produce new cells

Chloroplast

Palisade mesophyll and spongy mesophyll: absorbs more sunlight to carry out the process of photosynthesis

Rough Endoplasmic Reticulum and Golgi Apparatus

Pancreatic cell: increases synthesis and secretion of digestive enzymes
Goblet cell in intestinal epithelium and respiratory tract: produces mucus
Liver cell: metabolises carbohydrates and detoxifies drugs and poisons

Failure of Cell Component

Failure of the mitochondrion function or a mitochondrion disjunction can cause stunted growth, weak muscles, hearing and vision problems
Tay-Sachs is a hereditary disease caused by the failure of enzymes to produce in the lysosomes
Tay-Sachs patients will experience stunted growth and mental retardation