CH. 3 Histology: The Study of Tissues

Tissues

groups of cells located in a distinct region of the body that works together to carry out a specific function.

A. Histology- the study of tissues

B. Tissues differ from each other based on the types of cells that they contain and the specific functions of those cells.

C. Tissues are most effectively observed using microscopes. In most cases, small tissues sections are removed from the body, stained, and prepared for observation on a microscope slide.

D. Tissues are often sectioned and stained for easy observation under the microscope.

What are the 3 sections for observation that tissue can be cut along?

1) A longitudinal Section

2) A Cross Section (Transverse Section)

3) An oblique Section

Types of Tissues in the Human Body

A) Epithelial Tissue

B) Connective Tissue

C) Muscle Tissue

D) Nerve Tissue

Epithelial Tissue (Epithelium-singular)

occurs has a sheet of cells that covers or lines surfaces and cavities in the body.

General Features of Epithelial Tissue

1) The cells of epithelium are arranged in sheets and are packed closely together.

2) It is avascular (does not contain blood vessels). Epithelial cells are nourished by nutrients that diffuse from blood vessels in the underlying connective tissue.

3) Epithelium has a nerve supply

4) Epithelium has a high regeneration rate. Cell division occurs rapidly in epithelial cells. This allows epithelial tissue to heal quickly.

5) Epithelial tissue has several major functions in the body including: protection, absorption, filtration, excretion, secretion and sensory reception.

6) Nearly all substances received or given off by the body must pass through a layer of epithelial tissue.

Structure of Epithelial Tissue

1) The Apical Surface

2) All epithelial tissues rest upon and are supported by connective tissue.

The Apical Surface

upper, free surface of epithelial tissue that is exposed to the exterior or to a body cavity.

• This layer may contain fingerlike projections called microvilli or hair like structures known as cilia.

  • These referred to as a brush border and they aid in increasing the surface area of the tissue.

Basement membrane

a layer of attachment between epithelial and connective tissue

• Functions by holding epithelial tissue in place.

• A key role in regulating the movement of materials between the epithelium and the lower connective tissue

2 Layers of the Basement Membrane

A) Basal lamina

B) Reticular lamina

Basal lamina

secreted by the epithelial tissue.

• Acts as a filter that determines which molecules will diffuse from underlying connective tissue.

• Composed primarily of proteins and sugars, it is acellular.

  • Referred to as the basal surface.

Reticular lamina

secreted by connective tissue.

• functions by providing support to the overlying epithelial tissue.

Arrangement of Cells in Epithelial Tissue- an organization of cells in epithelial tissue

1) Simple epithelium

2) Stratified epithelium

3) Pseudostratified epithelium

Simple epithelium

is only one cell layer thick

• found in areas where absorption, filtration, and osmosis occurs.

Stratified epithelium

is composed of two or more cell layers.

• found in areas where protection is important.

Pseudostratified epithelium

has the appearance of being several cell layers thick

• only one cell layer thick

Cells Shapes in Covering and Lining Epithelium

A) Squamous cells

B) Cuboidal cells

C) Columnar cells

D) Transitional cells

Squamous cells

are flat and scalelike

Cuboidal cells

are boxlike, almost as tall as they are wide

Columnar cells

are column or rectangular in shape.

Transitional cells

have the ability to change shape.

Two Broad Categories of Epithelial Tissue (both are further subdivided into specific types)

1) Simple Epithelium

2) Stratified Epithelium

Specific Types of Simple Epithelium

1) Simple Squamous epithelium

2) Simple cuboidal epithelium

3) Simple columnar epithelium

Simple squamous epithelium

composed of a single layer of flat cells

a) is a very thin tissue, so it is highly adapted for diffusion and filtration.

b) Forms endothelium, which lines blood vessels and many of the hollow organs of the body.

c) Mesothelium- serous membrane that covers the ventral body cavity

D) the most abundant epithelial tissue in the body

E) Specific functions of this tissue include allowing for rapid diffusion and secreting serous fluid.

Exfoliation

the loss of simple squamous epithelium from the surface

Simple cuboidal epithelium

lines glands and is involved in secretion and absorption

• found in the kidney tubules.

Simple columnar epithelium

A) can be nonciliated (as in the gallbladder) or ciliated (as in the Fallopian tubes- the cilia here move eggs to the uterus)

B) is often covered by microvilli

C) lines the digestive system from the mouth to the anus

D) Contains goblet cells which produce mucus.

Specific Types of Stratified Epithelium

1) Stratified Squamous Epithelium

2) Stratified Cuboidal Epithelium

3) Urothelium

Stratified Squamous Epithelium

A) can be keratinized (covered by the thick protein keratin or nonkeratinized)

B) Keratinized squamous epithelium makes up the bulk of the epidermis while nonkeratinized squamous epithelium forms a covering over the tongue.

C) Keratinized stratified squamous epithelium resists abrasions and water loss. Nonkeratinized stratified squamous epithelium protects the body from pathogenic organisms.

Keratinized squamous epithelium

• Makes up the bulk of the epidermis

• resists abrasions and water loss

Nonkeratinized stratified squamous epithelium

• forms the covering of the tongue

• protects the body from pathogenic organisms.

Stratified Cuboidal Epithelium

lines the sweat glands and a portion of the ovaries.

• Capable of secreting numerous hormones in the body.

Urothelium

is composed of cuboidal cells that often bulge above the apical surface.

• located in the kidney and ureter

• Has an ability to stretch beyond its normal size.

• Thick and often serves as a protective tissue over body surfaces.

Pseudostratified epithelium

looks thick bit is only one cell layer thick.

• Pseudostratified columnar epithelium

Pseudostratified columnar epithelium

located in the trachea and nasal cavity.

Contains:

• Goblet cells

• Cilia

Connective Tissue

the most abundant type of tissue in the human body.

Functions of Connective Tissue

1. Binds structures together
2. Provides support
3. Protects, provides immunity
4. Insulates, pads
5. Transports materials through the body
6. Movement
7. Storage
8. Some heat production

General Features of Connective Tissue

1) Has an extensive nerve supply

2) Most types are highly vascular

Structure and Organization of Connective Tissue

connective tissues is composed of 3 basic elements

a) cells

b) Fibers

c) matrix

d) Mesenchyme

Cells

make up the bulk of most connective tissues.

1) Prefix blast- refers to unspecialized, immature types of connective tissue embryonic cells.

• Typically, blasts become cytes.

  • Ex. fibroblasts

2) Suffix -cyte refers to mature types of connective tissue cells

Fibers

provides support and strength to connective tissue

• Collagen elastic fibers and reticular fibers are 3 major types of fibers found in connective tissue.

  • composed of various proteins

1) Collagen fibers

2) Reticular fibers

3) Elastic fibers

Collagen fibers

are extremely strong and resist stretching

• These fibers are abundant in the skin, bones, and cartilage of the body

Reticular fibers

form an internal framework for several organs

• the spleen and lymph nodes

Elastic fibers

composed of the protein elastin and have the ability to stretch as needed.

• abundant in the connective tissue associated with the lungs and arteries of the body

Matrix

the material that surround connective tissue cells.

• noncellular

• It can be fluid, gelatinous or solid

• Ground substance- fills the space around the connective tissue cells

Ground substance

fills the spaces around the connective tissue cells

• composed of matrix and fibers

Mesenchyme

embryonic connective tissue

• develops early in embryonic development and specializes into the different connective tissues that make up the body

• some remains in the human body throughout our lives

Types of Connective Tissue in the Body

1) Areolar Connective Tissue

2)Adipose Tissue

3) Reticular Tissue

4) Dense Regular Connective Tissue

5) Dense Irregular Connective Tissue

6) Cartilage

7) Bone (Osseous) Tissue

8) Blood

Areolar Connective Tissue

contains all 3 types of connective tissue fibers

• provides strength, support, and elasticity to body structures

• Found beneath epithelial tissue

• Plays a role in anchoring the epithelium in place

• Serves as a packaging tissue in the body

• if inflamed, areolar tissue soaks up the excess fluid to prevent edema

• classified as a type of loose connective tissue

• Can be stronger than steel

Adipose Tissue

fat tissue

a) Adipocytes- mature cells in adipose tissue. Specializes for fat storage. Fat is stored in a fat vacuole

b) functions as an insulator, a source of stored energy and as a padding around body storage

c) classified as a loose type of connective tissue

d) Subcutaneous layer- composed of areolar and adipose tissue. Attaches the skin to the underlying tissues and muscles.

e) white fat- typical fat in an adult

f) brown fat tissue- found primarily in a developing fetus and remains in the infant after birth for a long period of time. Get it color from the abundant supply of blood vessels found in the tissue itself. Brown fat generators heat that warms the fetus and infant

Adipocytes

mature cells in adipose tissue

• specialized for fat storage

• The fat is stored in a fat vacuole

Subcutaneous layer

composed of areolar and adipose tissue

• attaches the skin to the underlying tissues and muscles

White fat tissue

typical fat in adults

Brown Fat Tissue

found primarily in a developing fetus and remains in the infant after birth for a period of time

• gets it color from the abundant supply of blood vessels in the tissue itself

• generates heat that warms the fetus and infant

Reticular Tissue

contains only reticular fibers and forms a loose connective tissue.

a) very abundant in many lymphatic structures; like the lymph nodes, spleen, and bone marrow.

• hold structures together and it can form a framework for blood cells to attach to

Dense Regular Connective Tissue

fibers in this tissue are pack tightly together.

• Contain collagen fibers; offers a great deal of strength

• provides strength and supply to body structure

• tendons- composed of dense regular connective tissue

  • connective tissue cords that attach muscles to bone

• ligaments- dense regular connective cords that attach bone to bone

Tendons

dense regular connective cord that attaches muscles to bone

Ligaments

dense regular connective cord that attaches bone to bone

Dense Irregular Connective Tissue

fibers have an irregular arrangement

• forms sheets that cover and protect organs and structures within the body

• found in heart valves and in the periosteum (membrane that covers bones)

• forms protective, fibrous coverings over some organs

Cartilage

composed of fibers that are packaged tightly together

• can withstand a great deal of stress

  A) Chondrocytes- mature cartilage cells.

  • located in open spaces known as lacunae

    • Matrix surrounds the lacunae

    • Perichondrium- the membrane that surround cartilage tissue

    • Cartilage- greatly reduced blood supply and nerve supply

      • Very slow growing and healing

B) Chondroblasts- secrete new cartilage matrix

• develop into chondrocytes

Chondrocyte

mature cartilage cells

• located in open space known as lacunae

  • Matrix surrounds the lacunae

  • Perichondrium- the membrane that surrounds cartilage tissue

Chondroblasts

secrete new cartilage matrix

• develop into chondrocytes

Types of Cartilage Tissue

1) Hyaline Cartilage

2) Elastic Cartilage

3) Fibrocartilage

Hyaline Cartilage

most abundant type of cartilage in the body

• located at the ends of long bones

• reduces friction and absorbs shock at the end of bones

• make up the bulk of the embryonic skeleton

• forms the epiphyseal plates of bones

• referred to a articular cartilage

Elastic Cartilage

similar to hyaline cartilage in structure

• form the bulk of the ears, nose, glottis (voice box), and epiglottis (flap that covers the trachea)

Fibrocartilage

forms pads in the human body

• can withstand extreme pressure

• Ex. intervertebral discs and the public symphysis

Bone (Osseous) Tissue

due to its hardness, bone has the ability to support and protect body structures

• stores calcium and phosphorous for body

• forms the skeleton of the body

2 Types of Bone Tissue

1) Compact Bone

2) Spongy Bone

Compact Bone

forms the external covering over all human bones

• composed of repeating units Haversian System (Ostenons)

Components of Haversian Systems

1) Osteocytes

2) Lamella

3) Canaliculi

4) Haversian (Central) Canals

Osteocytes

mature bone cells

• located in lacunae

Lamella

rings of matrix

• composed of mineral salts

  • Can be calcium carbonate or calcium phosphate

Canaliculi

small canals that extend from lacunae, through the lamellae of bone

• nutrients and wastes pass to/ from osteocytes through these small canals

Haversian (Central) Canals

holes in the center of each Haversian system.

• openings contain blood vessels and nerves

Spongy Bone

is not composed of Haversian systems

• composed of thin plates- Trabeculae

• Trabeculae are composed of osteocytes and lamellae

Bood

has a liquid matrix

Components of Blood

1) Plasma

2) Formed elements

Plasma

the liquid portion of blood

• the matrix of blood

• Contains a variety of of dissolved compounds

Formed Elements

cells and cell fragments in blood

• formed elements in the body include:

  • Erythrocytes (Red Blood Cells)

  • Leukocytes (White Blood Cells)

  • Thrombocytes (Platelets)

Erythrocytes (Red Blood Cells)

involved in carrying oxygen to the body cells and carbon dioxide to the lungs

• lack a nucleus and cannot divide.

• contain the red pigment hemoglobin

Leukocytes (White Blood Cells)

function in fighting infection and in providing immunity to the body

• have a distinct nucleus and can divide

Thrombocytes

involved in blood clotting

Muscle Tissue

composed of fibers that are capable of generating force from contraction

A) Function to move bones, provide body support and protection and thermogenesis (heat production)

B) compose of numerous cells- MUSCLE FIBERS

Types of Muscle Tissue in the Human Body

1) Skeletal Muscle Tissue

2) Cardiac Muscle Tissue

3) Smooth Muscle Tissue

Skeletal Muscle Tissue

attaches to and moves bones

• classified as being striated and voluntary

Cardiac Muscle Tissue

located in the wall of the heart

• is striated and involuntary

• contains intercalated discs- swelling of the cell membrane of cardiac muscle fibers

  • Hold cardiac muscle fibers together during muscle contraction

• responsible for pumping blood throughout the body

Smooth Muscle Tissue

located in the internal organs and blood vessels of the body

• Is nonstriated and involuntary

• regulates blood flow in and out of organs

• regulates movement within the digestive system

Nervous Tissue

makes up the brain, spinal cord and nerves of the nervous system

2 Types of Cell in Nervous System

1) Neuroglia (Support Cells)

2) Neurons

Neuroglia (Support Cells)

support, insulate and protect the nervous system

Neurons

the primary type of nerve cells

• capable of generating and conducting impulses (electric signals) throughout the body.

• Cannot divide

• function by responding to stimuli via impulse formation and conduction

Tissue Repair

the process by which tissues replace dead or damaged cells

A) Tissue repair can occur by regeneration and fibrosis

B) Epithelial and connective tissue have a high capacity for continuous renewal

C) Muscle tissue repair can occur, it is generally a slow process

D) Nerve tissue does not have much capacity for renewal

What are the 2 major ways tissue repair can occur?

1) Regeneration

2) Fibrosis

Regeneration

the replacement of destroyed tissue with the same kind of tissue

Fibrosis

the formation of fibrosis connective tissue (Scar tissue) over injured tissue

Conditions that Influence Tissue Repair

1) Tissue type

2) Nutrition- nutrients needed to direct healing of tissue include vitamins A, C, E and K

3) Proper Blood Circulation- carried oxygen, nutrients to the injury site

4) Age- young tissue generally repairs faster than older tissues

Tissue Growth

A) Hyperplasia

B) Hypertrophy

C) Neoplasia

D) Metaplasia

Hyperplasia

occurs as cells increase their number

• Epithelium grows in this fashion

Hypertrophy

occurs as preexisting cells enlarge in size

• adipose and muscle tissue

Neoplasia

development of a tumor (either benign or malignant)

• known as neoplasm (new growth)

Metaplasia

occurs when one type of tissue changes to another type of tissue (ciliated epithelium in smokers often changes to a stratified form of epithelium)