HLT31507 CERTIFICATE III IN NUTRITION & DIETETIC ASSISTANCE

CELLS & TISSUESdelivered by:

Mary-Louise Dieckmann

Cells

• Cells are the building blocks of life

• They are comprised of four elements:– Carbon– Oxygen– Hydrogen– Nitrogen

Structure of a Cell

Cells have three main parts:• The plasma membrane• The cytoplasm• The nucleus

The Nucleus

Control centre of a cell. It contains:• DNA – deoxyribonucleic acid

The Plasma Membrane

• is the outer boundary for the cell, also referred to as cell membrane

• Is arranged ‘tail to tail’• has a double phospholipid layer with– Hydrophilic heads (water loving)– Hydrophobic tails (water hating)

• contains proteins, cholesterol and gylcoproteins (sugar-proteins)

The Plasma Membrane

The Cytoplasm• is outside the nucleus but inside the plasma membrane• Contains:– Cytosol– Organelles– Inclusions

The Cytoplasm• The cytosol is the fluid that suspends other elements

• The inclusions are chemical substances (present depending on the type of cell)

The Organelles• Metabolic machinery of the cell. They include:– Mitochondria– Ribosomes– Endoplasmic Reticulum (rough and smooth)– Golgi Apparatus– Lysosomes– Peroxisomes– Cytoskeleton– Centrioles

Organelles

The OrganellesMitochondria are the ‘powerplants’ of a cell– They carry out reactions where oxygen is used to break down food– Provide ATP for cellular energy

Ribosomes are the actual sites of protein synthesisThey are made of protein and RNA (riboxynucleicacid)

The OrganellesGolgi Apparatus is the ‘traffic director’ for cellular proteinsModifies and packages proteins for transportProduces different types of ‘packages’:• Secretory vesicles• Cell membrane components• Lysosomes

The Golgi Apparatus

The Organelles

Cytoskeleton is the framework that determines the cell shape

A network of protein structures

Provides the cell with an internal framework that helps to support other organelles

Allows transport and types of cellular movement

Cell Diversity

Two types of cells that connect body parts• Fibroblasts• Erythrocytes (red blood cells)

Cell Diversity• Epithelial cells cover and line body organs

Cell Diversity• Skeletal muscles and smooth muscle cells have contractile filaments designed for contraction that causes movement

Cell Diversity• Fat cells store nutrients

Cell Diversity• Macrophages or phagocytes fight disease. The lysosomes digest infectious micro-organisms

Cell Diversity• Nerve cells gather information and control body functions

Cell Diversity• Reproductive cells include oocytes and sperm

CHAPTER 3 – PART 2CELLULAR PHYSIOLOGY

Membrane Transport• Membrane transport – movement of substances into and out of the cell

• Two Transport Methods – passive (no energy) and active (metabolic energy provided by the cell)

Solutions• Intracellular fluid (found inside the cell)– cytosol and nucleoplasm

• Extracellular fluid (or interstitial fluid) (found outside the cell)– hormones, nutrients, neurotransmitters and waste products

Passive Transport

• Two types – diffusion and filtration

• Simple diffusion:– substances move from an

area of higher concentration to an area of lower concentrations

Passive Transport

• Facilitated (helped) diffusion – uses a carrier or a channel – Substances bind to

protein carriers– Moves through a

channel constructed by channel proteins

Passive TransportFiltration• water and solutes are forced through the membrane wall by pressure• Pressure can be caused by blood pressure ie. Kidney filtration.

Active Transport• Uses sodium-potassium pump to move ions against the concentration gradient• Requires ATP to energise the protein carriers

Active Transport

Active Transport

• Step 1 – Sodium enters the protein pump, and 1 ion of phosphate binds onto the pump, causing it to change shape

Active Transport

• Step 2 – The protein pump changes shape and then sodium ions (Na) are forced out of the cell.

• Next, potassium (K) ions bind onto the pump protein, and the phosphate ion lets go.

Active Transport

• Step 3 – this causes the pump protein to return to its original shape, and then potassium ions are released into the cell.

Exocytosis (out of the cell)• Bulk transport of substances – hormone, mucus or ejection of waste products

Endocytosis (into the cell)• Includes all of the ATP-fuelled processes• Vesicular sac forms, bringing ingested substance into cell• Lysosomes digest vesicle, releasing contents into cytoplasm

Endocytosis (into the cell)

CHAPTER 3 – PART 3BODY TISSUES

TissuesTissues are groups of cells that are similar in structure and function.Four primary tissue types:– Epithelial tissue– Connective tissue– Muscle tissue– Nervous tissue

Epithelial Tissue• Forms body coverings, body linings and glandular tissue• Major functions:– Protection– Absorption– Filtration– Secretion

Special Characteristics of Epithelial Tissue

• Closely packed cells• Always have apical (unattached) and basal (attached) surfaces• Innervated but avascular• Two names – first indicates number of layers, second describes the shape of the cell

Simple Epithelia

Stratified Epithelia• More than one layer. More durable than simple epithelia, mostly concerned with protection.

Pseudostratified Columnar Epithelium

• False (pseudo) impression of being stratified

Transitional Epithelia

Connective TissueMost abundant and widely distributed tissue in human bodyFunctions:• Binding and support• Protection• Insulation• Transportation

Connective Tissue Characteristics

• Blood supply varies – some are well vascularized and others have poor blood supply or are avascular

• Extracellular Matrix – non living material that surrounds living cells

Extracellular Matrix• Ground substance – mostly water, adhesion proteins & polysaccharide molecules• Fibers – provide support. Three types:– Collagen (providing high tensile strength) – Elastic (allowing stretch and recoil)– Reticular (fine fibers that form networks)

Major Classes of Connective Tissue

• Blood• Loose Connective Tissue • Dense Connective Tissue • Cartilage • Bone

Blood• Blood cells surrounded by fluid matrix (plasma)• Fibers visible during clotting• Functions as transport vehicle

Loose Connective TissueAreolar Connective Tissue• Most widely distributed connective tissue• Soft and pliable – ‘cob-web’ like• Contains all fiber types• Can soak up excess fluid

Loose Connective Tissue

Adipose (fat) Connective Tissue• Matrix is areolar tissue with

fat globules• Cells contain large lipid

deposits• Functions:– Insulates the body– Protects some organs (ie.

Kidneys)– Site of fuel storage

Loose Connective TissueReticular Connective Tissue• Delicate network of interwoven fibers• Forms internal supporting network (stroma) of lymphoid organs, including:– Spleen– Lymph nodes– Bone marrow

Dense Connective Tissue

• Major matrix element is collagen fibers

• Cells are known as fibroblasts

• Two major types:– Tendon (attach muscle to

bone)– Ligaments (attach bone to

bone)

Cartilage

Hyaline Cartilage• Most abundant

cartilage in body• Comprised of

collagen fibers and a rubbery matrix

• Entire fetal skeleton is hyaline cartilage

Cartilage

• Elastic Cartilage – provides strength and stretchability – ie. The external ear

• Fibrocartilage – highly compressible, providing cushioning – ie. The intervertebral discs

Bone

• Also know as osseous tissue• Protects and supports the

body• Comprised of:– Bone cells in lacunae– Hard matrix of calcium salts– Large numbers of collagen fibers

Muscle Tissue• Highly specialised to contract or shorten to produce movement.• Three major types:– Skeletal muscle– Cardiac muscle– Smooth muscle

Skeletal Muscle Tissue• Under voluntary control• Cells are striated, multi-nucleate• Attaches to the bones

Cardiac Muscle Tissue

• Only found in the heart• Involuntary• Cells are uninucleate and

striated• Cells attach to other

cardiac muscle cells at intercalated disks

Smooth Muscle Tissue

• Involuntary• No visible striations,

uninucleate• Surrounds hollow organs• Attaches to other smooth

muscle cells

Nervous Tissue• Two principal types:– Nerve Cells (Neurons)

Highly specialised in order to transmit nerve impulses. All have a cell body, nucleus and one or more fibers

– Supporting Cells (Neuroglia)Provide insulation, support and protection. They do not transmit nerve impulses and can divide… (unlike neurons)

Tissue Repair• Regeneration– Replacement of destroyed tissue by the same kind of cells

• Fibrosis– Repair by dense fibrous connective tissue (scar tissue)

• Determination of method – type of tissue and severity of the injury