• 2-How is the structure related to the function?

• The body contains at least 200 distinct cell types.

• These cells contain essentially the same internal structures yet they vary enormously in shape and function.

• The human body starts as a single cell at fertilization. As this fertilized egg divides, it gives rise to trillions of cells, each built from the same blueprint

Principal Tissue Types

• Epithelial (simple and stratified)• Connective• Muscular• Nervous

What is a tissue?

• Tissue– Groups of cells that are similar in structure and

function• Four Primary Types:

– Epithelium– Connective– Nervous– Muscle

• These tissues associate and interact to form organs with specialized functions

Tissue• Definition – an aggregation of cells in which

each cooperates with all others in the performance of a given function

• Examples of general functions– Protection– Control permeability– Sensation– Production of chemicals/ secretions

Tissues

• Cells are organized into sheets or groups called tissues.

• There are four major tissue types found in the body: epithelial tissue (ET), connective tissue (CT), muscle tissue, and nervous tissue.

• These tissues associate and interact to form organs with specialized functions.

Epithelial Tissue (ET)

• Epithelia are sheets of cells that function in protection, secretion, absorption, and excretion.

• Epithelium is composed of tightly packed cells anchored to a basement membrane.

• It lacks blood vessels and rapidly divides.• ET are classified by cell shape and number

of cell layers.

Classification of Epithelial Tissues

Simple Squamous Epithelium

It consists of a single layer of thin, flat cells that fit tightly.

Simple Squamous Epithelium

• consists of a single layer of thin, flat cells that fit tightly.

• functions in filtration, diffusion, osmosis, and covers surfaces.

• found in air sacs of the lung, walls of capillaries, lines blood vessels, and covers the membranes that line body cavities.

* Since it is only one layer of cells and very thin it allows diffusion of small molecules unlike stratified squamous epithelium

Simple Cuboidal Epithelium

It consists of a single layer of cube-shaped cells.

Simple Cuboidal Epithelium

• consists of a single layer of cube-shaped cells.• functions in secretion and absorption.• found on the surface of the ovaries, linings of

kidney tubules, linings of the ducts of certain glands.

Simple Columnar Epithelium (Fig. 5.3)

It is a single layer of elongated, column-shaped cells.

Simple Columnar Epithelium

• single layer of elongated, column-shaped cells.• functions in protection, secretion, and absorption

and can be ciliated or nonciliated.• specialized goblet cells secrete mucus.• found as lining of the uterus, stomach, and

intestines.

Pseudostratified Columnar ET (Fig.5.5)

It is a single layer of elongated cells that appears to be more than one layer.

• often ciliated• functions in protection, secretion, and movement of

mucus and cells.• found lining the respiratory passages, trachea.

Pseudostratified Columnar Epithelium

Stratified Squamous Epithelium (Fig. 5.6)

It consists of many layers of cells with flat cells on the outer layers.

Stratified Squamous Epithelium

• consists of many layers of cells with flat cells on the outer layers.

• functions in protection.• found in the outer layer of the skin, linings of the

oral cavity, throat, vagina, and anal cavity.

* Since it consists of many layers it acts as a barrier which prevents entry of pathogens into the human body through the epithelium

Stratified Cuboidal Epithelium (Fig. 5.7)

It consists of two to three layers of cubed-shaped cells.

Stratified Cuboidal Epithelium

• consists of two to three layers of cubed-shaped cells.

• functions in protection.• found in the linings of the mammary glands, sweat

glands, salivary glands, and pancreas

* see also glandular epithelium, textbook p. 138

Stratified Columnar Epithelium (Fig. 5.8)

It consists of a top layer of elongated cells, and lower layers of cube-shaped cells.

Stratified Columnar Epithelium

• consists of a top layer of elongated cells, and lower layers of cube-shaped cells.

• functions in protection and secretion.• found in the vas deferens, part of the male urethra,

and parts of the pharynx.

Transitional Epithelium (Fig. 5.9a)

It consists of many

layers of cube-shaped and elongated cells.

Transitional Epithelium

• It consists of many layers of cube-shaped and elongated cells.

• functions in distensibility and protection.• found in the inner lining of the urinary bladder,

ureters and part of the urethra.

Connective Tissues (CT)

• Connective tissue is the most abundant tissue in the body.

• Extracellular material, a matrix, makes up the bulk of the tissue.

• Matrix is composed of fibers and ground substance.

• Connective tissue cells usually can divide.

CT Cell Types

• Mast cells or basophils release heparin, which prevents blood clotting, and histamine, which aids in the inflammatory response.

CT Cell Types

• Fibroblasts secrete protein into the matrix, usually collagen which is a fibrous protein resulting in fibers.

CT Cell Types

• Macrophages originate as white blood cells. They can move and phagocytize foreign particles.

CT Fibers

• White collagenous fibers, are made of thick threads of collagen. They are strong, flexible, and inelastic.

• Elastic fibers, yellow fibers, are made of bundles of elastin.

Loose CT (Fig. 5.18)

• Loose CT or areolar tissue binds organs together and holds tissue fluids.

Loose Connective Tissue

• Loose CT or areolar tissue binds organs together and holds tissue fluids.

• It consists of cells (fibroblasts) in a fluid-gel matrix.• It forms thin membranes found beneath the skin,

between muscles, and beneath epithelial tissue.

Adipose Tissue

• Adipose tissue protects, insulates, and stores fat in droplets inside the cells.

Figure 5.19

Adipose Tissue

• Adipose tissue protects, insulates, and stores fat in droplets inside the cells.

• It consists of cells (adipocytes) in a fluid-gel matrix.• It is found beneath the skin, around the kidneys,

behind the eyes, and on the heart.

Reticular Connective Tissue

• Reticular connective tissue supports organs.

Figure 5.20

Reticular Connective Tissue

• Reticular connective tissue supports organs.• It is composed of thin, collagenous fibers and cells

in a fluid-gel matrix.• It is found in the walls of the liver, spleen, and

lymphatic organs.

Dense Connective Tissue

• Dense connective tissue binds organs together.

Figure 5.21

Dense Connective Tissue

• Dense connective tissue binds organs together.• It is composed thick collagenous fibers, thin elastic

fibers and fibroblasts in a fluid-gel matrix.• It is found in tendons, ligaments, and the dermis of

the skin.

Cartilage, a CT

• Cartilage is a rigid connective tissue.• The matrix consists of collagenous fibers in a gel-

like ground substance.• Cartilage cells, chondrocytes, are found in small

chambers, lacunae.• Cartilage is covered with a thin layer of CT, the

perichondrium.• Cartilage lacks blood vessels.

Hyaline Cartilage

• It supports, protects, and provides a framework.

• It is the most common type of cartilage.

Figure 5.23

Hyaline Cartilage

• It supports, protects, and provides a framework.• It is the most common type of cartilage.• It is found in the ends of bones, nose, and rings in

the respiratory passages.• Hyaline cartilage provides the embryonic model for

the skeleton.

Elastic Cartilage

• It supports, protects, and provides a flexible framework.

Figure 5.24

Elastic Cartilage

• It supports, protects, and provides a flexible framework.

• Its matrix contains many elastic fibers.• It is found in the outer ear and part of the larynx.

Fibrocartilage

• It supports, protects, and absorbs shock during body movement.

Figure 5.25

Fibrocartilage

• It supports, protects, and absorbs shock during body movement.

• It is the toughest type of cartilage.• It is found between the vertebrae (intervertebral

discs), in the knee and parts of the pelvic girdle.

Bone

• Bone supports, protects, provides a framework for muscle attachment.

Figure 5.26

Bone

Bone

• Bone supports, protects, provides a framework for muscle attachment.

• It is composed of cells (osteocytes) in a hard calcified matrix. The osteocytes are located in layers, lamellae, organized into osteons.

• It is found in the skeleton and middle ear.

Blood

• Blood transports gases, nutrients, and wastes, defends against disease, and acts in clotting. Figure 5.27

Blood

• Blood transports gases, nutrients, and wastes, defends against disease, and acts in clotting.

• It is composed of cells and platelets in a fluid matrix, the blood plasma.

• It is found within the blood vessels.

Muscle Tissue (MT)

There are three types of muscle tissue: skeletal, smooth, and cardiac.

Properties:• It is contractile (muscle fibers can shorten and

thicken).• It is excitable.

Skeletal Muscle

• It attaches to bones and is controlled by conscious effort.

• It is also called voluntary muscle.

Figure 5.28

Skeletal Muscle

• It attaches to bones and is controlled by conscious effort.

• It is also called voluntary muscle.• The muscle cells have many nuclei and exhibit light

and dark banding patterns called striations.• Skeletal muscles contract in response to nerve

signals.

Smooth Muscle

• It appears smooth because it lacks striations.

• Smooth muscle action is not under conscious control and it is called involuntary. Figure 5.29

Smooth Muscle

• It appears smooth because it lacks striations.• Smooth muscle action is not under conscious

control and it is called involuntary.• The cells are spindle-shaped with a central nucleus.• Smooth muscle is found in the stomach, intestines,

uterus, and blood vessels.

Cardiac Muscle

• Cardiac muscle tissue is found only in the heart.

Figure 5.30

Cardiac Muscle

• It is found only in the heart.• The striated cells are joined end to end with a

specialized intercellular junction called an intercalated disk.

• Cardiac muscle is under involuntary control.

Nervous Tissue (NT)• It is

excitable, but not contractile.

Figure 5.31

Nervous Tissues

• Nervous tissue is excitable like muscle tissue.• It is found in the brain, spinal cord, and peripheral

neurons.• Nerve cells or neurons sense changes and transmit

signals.• Neuroglia are cells that support and bind nervous

tissue. They supply nutrients, carry on phagocytosis, and play a role in cell to cell communication.

END

Picturing Mitosis and Meiosis

Do Now: compare these two, how are they similar? How are they different?

Mitosis Steps

1. Parent cell (duplicates / copies / replicates) its DNA

2. Cell divides into 2, DNA is divided into 2 daughter cells

Mitosis

1. Parent cell (duplicates / copies / replicates) its DNA2. Cell divides into 2, DNA is divided into 2 daughter cells

Meiosis Steps

1. Parent cell replicates its DNA

2. Cells and DNA divide into 2 cells.

3. Cells and DNA divide again for a total of 4 daughter cells.

Meiosis creates variation

• Crossing-Over

Using The List of Organelles Illustrate a functional analogy of a cell

1. Cell membrane2. Cytosol3. Cytoskeleton4. Nucleus5. DNA6. RNA7. Smooth ER8. Rough ER

9. Ribosomes10.Mitochondria11.Lysosomes12.Peroxisomes13.Golgi Apparatus

Include a key explaining your analogy.

Cytoplasmic Division

• Also known as cytokinesis • Begins during anaphase• Continues through telophase• Contractile ring pinches cytoplasm in half

Control of Cell Division

• Cell division capacities vary greatly among cell types• Skin and blood cells divide often and continually• Neuron cells divide a specific number of times then cease

• Chromosome tips (telomeres) that shorten with each mitosis provide a mitotic clock

• Cells divide to provide a more favorable surface area to volume relationship

• Growth factors and hormones stimulate cell division• Hormones stimulate mitosis of smooth muscle cells in uterus• Epidermal growth factor stimulates growth of new skin

• Tumors are the consequence of a loss of cell cycle control

• Contact (density dependent) inhibition

Tumors

• Two types of tumors:• Benign – usually remains localized• Malignant – invasive and can

metastasize; cancerous

• Two major types of genes cause cancer:• Oncogenes – activate other genes

that increase cell division• Tumor suppressor genes – normally

regulate mitosis; if inactivated they are unable to regulate mitosis

• Cells are now known as “immortal”

Normal cells(with hairlike cilia)

Cancer cells

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

© Tony Brain/Photo Researchers, Inc.;

Stem and Progenitor Cells

• Stem cell:• Can divide to form two new stem cells

• Self-renewal• Can divide to form a stem cell and a progenitor cell• Totipotent – can give rise to every cell type• Pluripotent – can give rise to a restricted number of cell types

• Progenitor cell:• Committed cell• Can divide to become any of a restricted number of cells • Pluripotent

Stem and Progenitor Cells

one or more steps

Sperm

Egg

Fertilizedegg

Stem cell

Stem cell

Progenitor cell

Progenitorcell

Progenitorcell

Blood cells and platelets

Fibroblasts (a connective tissue cells)

Bone cells

Progenitorcell

Astrocyte

Neuron

Skin cell

Sebaceousgland cell

produces another stem cell(self-renewal)

Progenitorcell

Progenitorcell

Progenitorcell

Progenitorcell

Progenitorcell

Progenitorcell

Cell Death

Apoptosis:

• Programmed cell death

• Acts as a protective mechanism

• Is a continuous process