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
READONLY!!
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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 - 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