Principles of Biology

By

Frank H. Osborne, Ph. D.

Cells and Tissues

Cells and Tissues• Living things exhibit structure and organization. The basic unit of structure and function is the cell.

• Cells are organized into units containing similar cells. These are called tissues.

• Different types of tissues are found in an organ. Organs are organized into units of structure called organ systems.

Cells and TissuesA living creature, such as a human, is an organism containing various organ systems with their component organs.

PLANT TISSUESI. Meristematic tissues

A. Shoot tip

B. Root tip

C. CambiumII. Permanent tissues

A. Surface tissues

1. Epidermis

2. Periderm

PLANT TISSUESB. Fundamental tissues

1. Parenchyma2. Collenchyma

3. Sclerenchyma

4. Endodermis

C. Vascular tissues1. Xylem

2. Phloem

PLANT TISSUES

Meristematic Tissues•Meristematic tissues have embryonic, undifferentiated cells. Undifferentiated means that these cells have not changed into other cells yet. When they do change, the process is called differentiation because the cells become different.

• The shoot tip meristem is found on the end of each branch. It is protected by a bud. This meristem produces all the tissues in the branch.

The Shoot Tip Meristem

The Root Tip Meristem

Meristematic Tissues• The root tip meristem is found on the tip of each root. It divides and produces all the cells found in the root.

• The cambium is found between the xylem (wood) and phloem (bark) of the tree. It is active only during the growing season, producing new xylem and phloem cells. This annual growth forms in rings.

Permanent Tissues• Epidermis contains living cells and is found on the surfaces of young stems and leaves.• The lower epidermis of leaves contains specialized occlusive cells called guard cells that surround openings in the leaves called stomates. •The stomates permit exchange of gases (carbon dioxide and oxygen) with the air outside of the leaf. The guard cells prevent loss of water.

Onion skin epidermis

Low Power (100x) High Power (400x)

Permanent Tissues

• Periderm contains non-living cells that have thick secondary walls. The walls are made waterproof with a material called suberin.

• Periderm tissue replaces epidermis on older stems of the plant. It prevents loss of water.

Periderm

Fundamental Tissues

• Parenchyma contains living cells that are capable of cell division. It is the least specialized of the plant tissues. These cells have thin primary walls. Parenchyma is used as a filler tissue in such plant structures as corn stalks.

Fundamental Tissues

• Collenchyma cells are usually alive. They have cell wall material that is deposited in the corners giving them a characteristic microscopic appearance. It serves as a support tissue in certain types of stems.

Parenchyma and Collenchyma

Fundamental Tissues

• Schlerenchyma cells are dead. They have thick secondary walls.

–Fibers are very long with thick walls and very small lumens. They provide vertical support structure in stems.–Sclereids are also dead. They have thick walls with very tiny interior spaces. They are parts of such plant structures as peach pits.

Sclerenchyma cells

Sclerenchyma fibers Sclereids

Fundamental Tissues

• Endodermis is a layer of living cells found in the root. It has a waterproofing layer known as the Casparian strip containing lignin and suberin.

• The plant uses the endodermis to regulate what materials enter the plant and are transported up to the stem and leaves.

Endodermis

Endodermis

Vascular TissuesVascular tissues are specialized transport tissues. There are two kinds: xylem and phloem.• Xylem cells are dead. Xylem transports water and nutrients upward in the plant.• Phloem has living cells. Phloem cells come in pairs, the sieve tube and the companion cell. The sieve tube transports conducts materials both upwards and downwards in the plant. Phloem is the major component of the bark of the tree.

Xylem

Phloem

ANIMAL TISSUESI. Epithelium

A. Simple epithelium1. Simple squamous epithelium2. Simple cuboidal epithelium3. Simple columnar epithelium

B. Stratified epithelium1. Stratified squamous epithelium2. Stratified cuboidal epithelium3. Stratified columnar epithelium

ANIMAL TISSUESII. Connective tissue

A. Tissues that connect body structures1. Loose connective tissue (areolar)2. Dense connective tissue3. Adipose (fat) tissue4. Cartilage

B. BoneC. Vascular tissue

1. Blood2. Lymph

ANIMAL TISSUESIII. Muscle

A. Smooth muscleB. Striated muscleC. Cardiac muscle

IV. Nerve

Simple Epithelium

Simple epithelium always contains a single layer of cells attached to a membrane. As this membrane is underneath the cells, it is called the basement membrane. There are three kinds of epithelium that differ in their shapes.

Simple EpitheliumSimple Squamous Epithelium

"Squamous" means flat. Simple squamous epithelium contains a single layer of flat cells attached to a basement membrane. An example is peritoneum, the tissue that surrounds and suspends the digestive organs in the abdominal cavity.

Simple EpitheliumSimple Cuboidal Epithelium

"Cuboidal" means having the shape of a cube. This tissue contains a single layer of cube-shaped cells on a basement membrane. An example of this type of tissue is the lining of the collecting duct in the kidney.

Simple EpitheliumSimple Columnar Epithelium

"Columnar" means that the cells are tall like columns. This tissue contains a single layer of tall cells on a basement membrane. An example of this type of tissue is the intestinal lining.

Stratified Epithelium

"Stratified" means that the cells of the tissues are found in layers. All three types of stratified epithelium start out as several layers of cuboidal cells on a basement membrane. The other layers determine which type of tissue it is.

Stratified EpitheliumStratified Squamous Epithelium

Stratified squamous epithelium contain several layers of cuboidal cells that flatten as you proceed away. An example is skin.

Stratified EpitheliumStratified Cuboidal Epithelium

In stratified cuboidal epithelium, the cells in all layers of the tissue are cuboidal. An example is the lining of the ducts of the sweat glands.

Stratified EpitheliumStratified Columnar Epithelium

In stratified columnar epithelium, all layers are cuboidal except for the top layer which contains tall cells. An example is the lining of the ducts of the mammary glands.

Connective TissueConnective implies holding things together or joining things. Thus we expect to find tendons, ligaments and cartilage classified as connective tissue. In addition, the category of connective tissue also contains body-wide tissues such as bone, blood and lymph. In most cases, the cells that make up the tissue are surrounded by some kind of matrix or material characteristic of the tissue.

Connective TissueAreolar (Loose) Connective Tissue

Loose connective tissue contains cells surrounded by a matrix of collagenous fibers, elastic fibers and lymph. Collagenous fibers are made of collagen, a type of structural body protein. Lymph is also called tissue fluid. It is a liquid that is found in between the different parts of the body in the spaces known as connective tissue spaces.

Connective TissueAreolar (Loose) Connective Tissue

Collagenous fiber

Elastic fiber

Fat cellLymphoblast

Lymph

Loose Connective Tissue

Connective TissueDense Connective Tissue Dense connective tissue is made of collagenous fibers. It is found in the dermis of the skin, tendons and ligaments. A tendon connects a muscle to a bone while a ligament connects one bone to another bone.

Dense Connective Tissue

Connective TissueAdipose Tissue (= Body Fat)Adipose tissue is made of fat cells. Each cell has a thin ring of cytoplasm that surrounds a large vacuole containing a fat droplet.

Connective Tissue

Connective TissueCartilage

There are three kinds of cartilage. Each consists of cells surrounded by a matrix of small fibers.• Yellow elastic cartilage is found in the arteries and between the rungs of the trachea.• Hyaline cartilage forms the ridge of the nose and the rungs of the trachea.• Elastic cartilage is found in the external ear, the epiglottis and the Eustachian tube.

Elastic Cartilage

Connective TissueCartilage• Hyaline cartilage forms the ridge of the nose and the rungs of the trachea.

Connective TissueBoneBone cells are surrounded by a matrix of calcium phosphate. There are tunnels in the bone called Haversian canals that contain the blood supply. Bone has the most mineral matter.

Connective TissueBoneThere are two types of bone called spongy bone and compact bone. • The ends of the long bones are made of spongy bone. "Spongy" means having the appearance of a sponge. • Compact bone does not have spaces in it that give it a spongy appearance. The long parts of the long bones are made of compact bone tissue.

Connective TissueVascular TissueVascular tissue consists of cells surrounded by a liquid matrix. There are two types of vascular tissue called blood and lymph.• Blood is found in blood vessels. It is carried by the circulatory system.• Lymph consists of fluid that is found outside of the blood vessels. It is also known as tissue fluid. It is collected via the lymphatic system and eventually returns to the circulatory system.

Blood

MuscleSmooth Muscle

Smooth muscles are found in all involuntary organs except the heart. Examples of organs include the diaphragm and the arteries. Smooth muscle does not contain striations.

Smooth Muscle

MuscleStriated Muscle•Striated muscles are attached to the bones of the skeleton. Each striated muscle cell is multinucleate because it has many nuclei. • Striated muscles contain striations, which are lines that produce a cross-banding effect. These lines result from the orientation of the muscle proteins within the cells. The striated muscle cells are also known as voluntary muscles.

MuscleStriated Muscle

Striated muscles contain striations, which are lines that produce a cross-banding effect.

Nucleus

Striation

Striated Muscle

MuscleCardiac Muscle

The heart is the only organ that contains cardiac muscle. This muscle cell type has distinct cells that are separated by intercalated discs. The intercalated discs partition the muscle into cells. Cardiac muscle cells also contain striations.

Muscle

Cardiac (Heart) Muscle

Properties

• One nucleus per cell• Striations• Involuntary

NucleusStriation

Intercalated disc

Cardiac Muscle

NerveNerve cells

The neuron is the cell of the nervous system. Each axon is surrounded by a sheath of membranes.

Dendrites

Nucleus

AxonTerminalBranches

SheathCell Body

Nerve Tissue Art

Nerve Tissue

The End

Principles of Biology

Cells and Tissues