chapter 5 tissues. histology the science that deals with the study of tissues
TRANSCRIPT
Chapter 5
TISSUES
HISTOLOGY
• The science that deals with the study of tissues
PATHOLOGIST
• Scientist who specializes in laboratory studies of cells and tissues to help physicians make accurate diagnoses
Four basic types of tissues
Epithelialcovers body surfaces, lines body
cavitiesConnective
protects and supports, binds organs together, stores energy
Musclegenerates force
Nervousinitiates and transmits impulses
Epithelial tissue
• Closely packed• Arranged in continuous sheets• Have a free (superficial) surface, exposed to a
body cavity• Have a basement membrane• No vascular tissue; exchange of materials is by
diffusion with connective tissue• Have nerve supply• High capacity for renewal• Functions include; protection, secretion,
absorption, excretion, sensory reception, generation of gametes
Covering and lining epithelium
• Four basic shapes:– Squamous
• flat
– Cuboidal• cubes
– Columnar• Tall cylindrical
– Transitional• Range in shape from flat to columnar; often
change shape due to distention
• Arrangement of layers:– Simple
• single
– Stratified• Two or more layers
– Pseudostratified• One layer; but appears to have many
Simple squamous
• Found where filtration or diffusion are priority
• Air sacs of lungs; walls of capillaries; covers membranes of body cavities
• Thin, delicate; easily damaged
Simple cuboidal
• Functions of secretion and absorption
• Found in kidney tubules, many excretory ducts of glands
Simple columnar
• Two forms: • Ciliated
– Cilia– Upper respiratory tract,
uterine tubes (oviducts)
• Nonciliated– Contains absorptive
cells (w/ microvilli) and goblet cells (secrete mucus)
– Linings of digestive, respiratory, reproductive
Stratified squamous• Superficial cells flat;
deep cells vary from cuboidal to columnar
• Forms outer layer of skin; lines oral cavity, esophagus, vagina, anal canal
• Keratinized – Contain keratin-tough
protein resistant to friction; helps repel bacteria
• Nonkeratinized– No keratin; remains
moist
Stratified cuboidal
• Function: protection, in some locations; secretion and absorption
• Sweat glands, mammary glands, salivary glands, pancreas
Stratified columnar
• Uncommon• Functions in
protection and secretion
• Found in male urethra, vas deferens, parts of pharynx
transitional
• Varies in appearance• Looks similar to
stratified cuboidal; except superficial cells are large and rounded
• Urinary bladder• Allows organs to
stretch w/out rupturing; helps prevent contents from diffusing back into internal environment
Pseudostratified columnar
• Nuclei of cells are at various depths; all cells are attached to basement membrane in a single layer
• Commonly have cilia• Lines passageways of
respiratory system
Pseudostratified
Connective Tissue
• Bind structures, • provide support and protection, • serve as frameworks, • fill spaces, • store fat, • produce blood cells, • protect against infection, • help repair tissue damage
CT general features
• Cells are farther apart then epithelial cells• Consists of 2 basic elements
– Cells– Extracellular Matrix
• consists of:– protein fibers – ground substance
» Consists of nonfibrous protein, other molecules, and fluid » Maybe fluid, semifluid, gelatinous, fibrous, calcified
• Does not occur on free surfaces• has nerve supply (exception cartilage)• Usually highly vascular (exception cartilage,
avascular and tendons, scanty blood supply)
CT cells
Each major type of CT cell contains immature cells (-blast)
• Blasts –have ability to divide; secrete matrix– fibroblasts= loose and dense CT– Chondroblasts= cartilage– Osteoblasts= bone
Cartilage and bone
• Once matrix is produced fibroblasts change into mature cells (-cyte)
• Do not divide or form matrix like -blasts– Chondrocytes– Osteocytes
Types of cells in CT• Fibroblasts
– Large flat spindle shaped w/ branching processes– Found in all CT– Most numerous cell in CT– Migrate thru secreting fibers and ground substance
• Macrophages– Irregular shape cell w/ short branching projections– Engulf bacteria and cellular debris
• Plasma cells– Small, either round or irregular– Secrete antibodies– Reside in CT, especially GI tract and mammary glands
• Mast cells– Abundant alongside blood vessels that supply CT– Produce histamine-dilates sm blood vessels, reaction to injury, infection
• Adipocytes– Fat cells; found below skin, around organs
• White blood cells– Not found in significant #’s in normal CT
CT matrix
• Ground substance plus protein fibers– Ground substance:
• Contains assortment of large molecules; many are complex combinations of polysaccharides and proteins
– Fibers:• Strength and support CT• 3 types embedded in matrix between cells:
– Collagen fibers– Elastic fibers– Reticular fibers
Collagen fibers
• Strong and resist pulling forces; not stiff- promotes tissue flexibility
• Occur in bundles lying parallel to each other
• Consist of protein- collagen• Most abundant protein in your body• Found in most types of CT (bone,
cartilage, tendons, ligaments)
Elastic fibers
• Smaller in diameter than collagen fibers
• Branch and join together to form a network
• Consist of protein (elastin) surrounded by glycoprotein (fibrillin)
• Strong but can be stretched• Plentiful in skin, blood vessel walls,
lung tissue
Reticular fibers
• Consisting of collagen and coating of glycoprotein
• Provide support in walls of blood vessels and form branching networks around fat cells, nerve fibers, skeletal and smooth muscle cells
• Produced by fibroblasts, much thinner than collagen fibers
• Form supporting framework of many soft organs
• Help form basement membrane
Classification of CT
Connective tissue proper:– Loose – DenseSpecialized connective tissue:– Cartilage– Bone– Blood– Lymph
Loose CT
• Areolar CT– Subcutaneous layer– Attaches skin to underlying tissues
• Adipose tissue– fat
• Reticular CT– Forms stroma (bed or covering) of
certain organs– Helps bind together smooth muscle
Dense CT
• Dense regular CT– Silvery white and tough– Tendons, most ligaments
• Dense irregular CT– Occurs in sheets– Dermis, heart valves, perichondrium
(membrane surrounding cartilage), periosteum (membrane surrounding bone)
• Elastic CT– Yellowish color; lung tissue, elastic arteries
Cartilage
• Hyaline– Bluish-white, shiny– Joints, epiphyseal plates (growth), nose
• Fibrocartilage– Strongest, lacks perichondrium– Discs between vertebrae
• Elastic– Maintains shape of certain structures
like external ear
Blood and lymph
• Blood= Liquid matrix• Lymph= clear fluid, similar to plasma
but w/ much less protein
Bone
• Organ composed of different CT– Bone or osseous tissue– Periosteum-tough, vascular covering on
outside of bone – Red and yellow bone marrow– Endosteum- membrane that lines space
w/in bone that stores yellow bone marrow
Basic unit of compact bone
• Osteon or Haversian system– Composed of:
• Lamellae– Concentric rings of matrix; mineral salts; collagen fibers
• Lacunae– Small spaces between lamellae; contains mature bone
cells (osteocytes)• Canaliculi
– Project from lacunae; network of small canals containing osteocytes provide routes for nutrients to reach osteocytes and wastes to leave
• Central (Haversian) canal– Contains blood vessels and nerves
Cancellous/Spongy bone
• No osteons• Columns of bone called trabeculae
– Which contain lamellae; osteocytes; lacunae; canaliculi
– Spaces between lamellae filled w/ red bone marrow