The Tissue Level of Organization

CHAPTER 4

Histology

Study of different tissues Abnormal cells and tissues can be

compared to normal tissues to identify disease, such as cancer

Being able to know and recognize normal tissues under the microscope is the first step

TIPS for studying histology

PRACTICE There are thousands of images, virtual labs and

practice quizzes online DON’T MEMORIZE

Tissues from the same organ will look vastly different RECOGNIZE PATTERNS

Don’t get lost in the big picture, look for patterns in how cells are organized

FORM = FUNCTION Keep in mind the function of the tissue and the organ

Introduction to tissues

Tissues are collections of cells and cell products that perform specific, limited functions

Histology = study of tissues There are 4 types of tissues

1. Epithelial – cover and protection2. Connective - support3. Muscle - movement4. Neural – signaling and communication

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Epithelial Tissue

Epithelial Tissue – General Info

Covers body surfaces and lines cavities Forms most glands Characteristics

Cells are tightly packed together Free surface exposed to environment = APICAL

SURFACE Attached to underlying connective tissue

(basement membrane) Avascular (no blood supply) – nutrients must diffuse Continually replaced at exposed surface

Epithelial Tissue - Function

1. Protection from abrasion, dehydration, destruction

2. Regulate gas and nutrient exchange3. Provide sensation4. Secrete substances such as sweat, hormones,

mucus and enzymes

Epithelial Tissue - Classification

1. First name indicates number of layers Simple: one layer of cells Stratified: more than one layer of cells Pseudostratified: appears to be stratified but is

not

Epithelial Tissue - Classification

2. Second name describes the shape of the cells

Squamous: thin and flat Cuboidal: cube shaped Columnar: tall, slender rectangles

Epithelial Tissue - Classification

Types of Epithelial Tissue

1. Simple Squamous▪ Description: single layer of flat cells▪ Functions: passage of material by simple diffusion

and filtration; secretes lubricating substances▪ Location: alveoli of lungs

Simple Squamous1. Simple Squamous

Simple squamous lining the

walls of the capillary

Types of Epithelial Tissue

2. Simple Cuboidal▪ Description: single layer of cube-shaped cells▪ Functions: absorption and secretion▪ Locations: Sweat glands, ducts, kidney tubules,

thyroid gland

Types of Epithelial Tissue

3. Simple columnar▪ Description: single layer, tall cells▪ Function: protection, absorption, secretion▪ Locations: Lining of the nasal passages, stomach

and intestines▪ Other: : Cells are very long and often have cilia

Types of Epithelial Tissue

4. Stratified Squamous▪ Description: many layers of flat cells (look at the

shape of the cells at the apical surface) ▪ Functions: Protection from abrasion, pathogens,

and chemicals▪ Locations: surface of skin, lining of mouth, throat,

esophagus, rectum, anus and vagina

Types of Epithelial tissue5. Pseudostratified ciliated columnar ▪ Description: single layer of columnar cells but the

position of the nuclei make it appear as there are many layers; often ciliated

▪ Functions: Protection and secretion▪ Locations: lining of nasal cavity, trachea and

bronchi and portions of male reproductive tract

Types of Epithelial Tissue

6. Transitional▪ Description: transitions from

one shape to the next; often has a scalloped apical edge

▪ Functions: permits expansion and recoil after stretching

▪ Locations: bladder, renal pelvis, ureters

Practice Identifying epithelial tissues

Pseudostratified

Practice Identifying epithelial tissues

Simple Squamous

Practice Identifying epithelial tissues

Simple Cuboidal

Practice Identifying epithelial tissues

Stratified Squamous

Practice Identifying epithelial tissues

TRANSITIONAL

Practice Identifying epithelial tissues

Simple Columnar

Connective Tissue

Connective Tissue - classification

1. Connective Tissue Propera) Loose Connective b) Adiposec) Dense Connective

2. Cartilaged) Hyalinee) Elasticf) Fibrocartilage

3. Other Tissuesg) Boneh) blood

Connective Tissue Proper

1. Loose Connective Tissue (Areolar Tissue)

Structure: More ground substance, less fibers

Functions: cushion, support, movement, defense against pathogens

Locations: between other tissues and organs, beneath skin, digestive, respiratory and urinary tracts, between muscles, around blood vessels, nerves and joints

1. Loose Connective Tissue (Areolar Tissue)

Connective Tissue Proper

2. Adipose (FAT) Structure: Fibroblasts enlarge and store fat,

very little matrix Functions: stores energy, insulates and

protects organs Locations: beneath the skin and around

organs especially at sides, buttocks, breasts, around eyes and kidneys

Connective Tissue Proper

2. Adipose Tissue

Connective Tissue Proper

3. Dense Regular (Fibrous) Structure: tightly organized bundles of

collagen Functions: Tendons (connect muscles to

bone) and Ligaments (connect bones to bones)

Dense Connective Tissue

3. Dense Regular

Dense Connective Tissue

Gel-type ground substance For shock absorption and protection No blood vessels Types of cartilage include

Hyaline cartilage Elastic cartilage Fibrous cartilage

Cartilage - characteristics

1.Hyaline Cartilage Most common Very fine, white collagenous fibers Covers ends of bones and joints and

respiratory passages

Types of Cartilage

2. Elastic Cartilage Elastic fibers in addition to collagen More flexible and elastic External ear

Types of Cartilage

3. Fibrous Cartilage (fibrocartilage) Very tough, large numerous collagen fibers Provides strong support and handles heavy

pressure Intervertebral discs

Types of Cartilage

Most rigid connective tissue Rigid due to mineral salts Bone cells called osteocytes Periosteum (Covers bone surfaces)

Bone (osseous Tissue)

MembranesHOMEWORK

Membranes – General Info Physical barriers Line internal spaces of organs and

tubes that open to the outside Line body cavities Different types of membranes\

Mucous Serous Cutaneous Synovial

Mucous Membranes

Mucous = protection Line passages that have external

connections Lining of digestive, respiratory, urinary

and reproductive tracts Epithelial surfaces are moist to

reduce friction and help absorption and excretion

Serous Membranes Line cavities not open to outside Are thin but strong Have fluid to reduce friction Three serous membranes

Pleura – lungs Peritoneum – abdomen Pericardium - heart

Cutaneous Membranes

Outer covering of body Skin Thick, waterproof and dry Stratified keratinized squamous

epithelium

Synovial Membranes

Line freely movable joint cavities Secrete synovial fluid into joint

cavity – provides lubrication Protects the end of bones Lacks a true epithelium

Muscle Tissue

Muscle Tissue – General Info Specialized for contraction Produces all body movement Three types

1. Skeletal2. Cardiac 3. Smooth

Muscle Tissue – Types1. Skeletal Muscle

Voluntary Cells are long, cylindrical, striated and

multinucleate Specialized for contraction

Muscle Tissue – Types2. Cardiac Muscle

Involuntary Cells are short, branched

and striated usually with a single nucleus

Found only in the heart

Muscle Tissue – Types3. Smooth muscle

Involuntary Cells are short, spindle-shaped and non-

striated with a single central nucleus Walls of hollow, contracting organs (blood

vessels digestive, respiratory, urinary and reproductive tracts)

Nervous Tissue

Nervous Tissue – General Info

Specialized for conducting electrical impulses

Rapidly senses internal or external environment

Processes information and controls responses

Concentrated in the central nervous system Brain and spinal cord

Two kinds of neural cells Neurons = neurons Neuroglia = supporting cells

Tissue Injury, Repair and Homeostasis

Tissues respond to injury to maintain homeostasis

Inflammation

Inflammatory response The tissue’s first response to injury Signs and symptoms of the inflammatory

response Swelling, redness, heat, pain

Can be triggered by Trauma (physical injury) or infection

Regeneration

Fibroblasts produce dense network of collagen fibers (scar tissue)

Most successful in… epithelia, connective tissues and smooth

muscle Least successful in…

Neural tissue, cardiac muscle

Aging and Tissue Structure Speed and efficiency of tissue repair

decrease with age due to Slower rate of energy consumption

(metabolism) Hormonal alterations Reduced physical activity

Osteoporosis – age related reduction in bone strength of women

Tissue ID

quizlet