Specialised Cells and Levels of Organisation

Lesson 12

Learning Objectives.

• Explain the structure and function of specialised cells: red blood cells, ciliated cells, palisade cells, xylem vessels, root hair cells, nerve cells, sperm cells, egg cells.

• Define the terms tissue, organ and organ systems with examples.

Red blood cells transport oxygen

cell surface membrane cytoplasm contains no nucleus

cytoplasm contains haemoglobin

bi-concave disc shape

allows more room for haemoglobin

increases surface area over which absorption of oxygen can occur

haemoglobin is a protein which carries the oxygen molecules

Ciliated cells move bacteria and dust away from the lungs

cilia

magnification X3000

nucleus

Cilia are small extensions of the cell. They beat rhythmically to sweep mucus, which has trapped bacteria and dust, away from the lungs

Root hair cells absorb minerals and water from the soil

cytoplasmcontains no chloroplasts as no photosynthesis is needed

root hairincreases surface area for absorption of water and mineral ions

Cross-section of a root hair cell

cell membrane semi-permeable, so will allow water and mineral ions into the cell

Xylem vessels transport water and minerals up the plant

xylem vessel

lignin

no cytoplasm

longitudinal sectioncross-section

water-proof and strong;helps support the plant

hollow: allows for continuous flow of water and dissolved mineral ions

xylem vessels are continuous tubes

Nerve cellsStructure:• These are extremely elongated

(long) cells• They have many branches at

both ends to connect to other nerve cells• The long axis (main branch) is covered in

fat to prevent the electrical impulses affecting the surrounding parts of your body

Function:• To carry nerve impulses around your body

Nerve Cells

Nerve cells transmit information in the form of electrical impulses

Direction of information

Match the cell type with the function.

Cell Type: Function:Ciliated cells conduction of water and supportRoot hair cells reproduction.Xylem vessels transport of oxygen.Palisade Cells movement of mucus in the

trachea.Nerve cells absorption.Red blood cells conduction of impulses.Sperm and Egg cells photosynthesis.

Levels of organisation

What you know so far:• Organelles – tiny structures found inside a cell.

» Nucleus, cytoplasm, ribosomes, etc.

• Cells – the basic unit of life.

A tissue is a group of cells of similar structure that perform a shared function

Animal tissues:muscle tissue

nervous tissue

upper epidermal tissue

palisade mesophyll tissue

spongy mesophyll tissue

lower epidermal tissue

Tissues found in the leaf

Cross-section of a leaf

An organ is a structure made of a group of tissues working together to perform specific functions

Plant organs include the stem and the leaves

heart

stomach

lungs liver

brain kidneys

An organ system is a group of organs that coordinate to perform related functions

In plants the shoot is an organ system consisting of leaves and the stem

lymphaticsystem

respiratorysystem

digestivesystem

excretorysystem

reproductivesystem

muscularsystem

skeletalsystem

nervoussystem

endocrinesystem

circulatorysystem

Levels of organisation

nerve cell nervous tissue

brain nervoussystem

Homo sapiens

smallest largest

cell tissue organ organsystems

organism

End of Chapter questions

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