Ch. 4Tissues
Objectives
• Define tissue
• Describe the four main tissue types
• Identify the various tissues that fall under the four main tissues types, their functions and composition
• Know how tissue growth and repair occur
Tissues
• Tissues– Group of cells that are similar in structure and
perform a common or related function
– The study of tissues and their arrangement into organs• Histology
– Four main types• Differ by type of cells and characteristics of matrix
Four Main Tissue Types
• Epithelial
• Connective
• Muscle
• Nervous
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science.tjc.edu
Epithelial Tissue
• Sheet of cells that covers a body surface or lines a body cavity– Covering and lining epithelium
• Cells that compose glands of the body– Glandular epithelium
• Functions– Protection, absorption, filtration, secretion,
excretion, sensory reception
Characteristics of Epithelium• Cellularity
– Almost entirely composed of closely-packed cells• Minimal ECF
• Specialized connections– Continuous sheet of cells– Tight junctions and
desmosomes
• Polarity– Apical surface and basal
surface– Basal lamina
• Connective tissue support– All epithelium supported by
connective tissue– Reticular lamina– Basal lamina + reticular lamina
= basement membrane
• Avascular– No blood vessels within
epithelium– Is innervated
• Regeneration– high regenerative capacity
Classification of Epithelium• Based on number of cell layers and on cell shape
• Cell layers– Simple – refers to one layer of cells– Stratified – refers to two or more layers of cells
• Cell shape– Squamous – flat, scale-like cells– Cuboidal – cube shaped cells– Columnar – column shaped cells
• How is pseudostratified columnar classified?
Simple Squamous Epithelium
• Thin and permeable– Found where rapid filtration and diffusion is
desired• Kidneys, lungs
unm.edu
Simple Cuboidal and Columnar
• Function in secretion and absorption
• Found in tubules of the kidneys and in ducts of glands
• Function in absorption and secretion
• Found in stomach, intestines, uterus, uterine tubes
uoguelph.ca faculty.palomar.edu
Pseudostratified Columnar Epithelium
• Function in secretion, absorption, and motility of mucus
• Cells vary in height, but all cells touch the basement membrane
• Found in the respiratory tract and male urethra
faculty.palomar.edu
Stratified Squamous• Most abundant stratified
epithelium
• Functions in protection against abrasion
• Found on outer layer of skin and extend a short way into every body opening that is continuous with the skin– Keratinized and non-keratinized
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Stratified Cuboidal and Columnar
• Functions in secretion and sperm production
• Found in sweat gland, ovaries, seminiferous tubules
• Function in protection and secretion
• Rare, found in ducts of large glands, male urethra
Transitional Epithelium
• Functions to allow distention of the urinary bladdery
• Found in the bladder
• Basal cells are typically cuboidal
• Apical cells vary in shapedspace.udel.edu
Glandular Epithelia• Glands are cells or organs that secretes a
substance for use or elimination– Originate from invagination of epithelial tissue
• Classified into two categories– Endocrine – Exocrine
• Unicellular glands– Composed of one cell that secretes its products into
its surroundings
Exocrine Glands
• Typically enclosed by fibrous capsule– Septa – capsular extension that divide gland into
lobes– Parenchyma – cells that synthesis and secrete
• Classified based on the duct– Simple – single unbranched duct– Compound – branching ducts
Exocrine Glands
Types of Secretions
• Serous glands– Thin watery fluids
• Mucus glands– Secrete mucin that is converted into mucus upon
absorption of water
• Cytogenic glands– Secrete whole cells
• Testes and ovaries
Epithelial Surface Features
• Three ways: Adhesion proteins, interdigitating folds, and specialized junctions
• Specialized junctions–Desmosomes–Tight junctions–Gap junctions
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Cell Adhesions
• Tight junctions • Gap junctions
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academic.brooklyn.cuny.edu
Epithelia Surface Features• Basal Features– Basement membrane
• Basal lamina
• Reticular fibers
• Apical Features– Microvilli
– Cilia
micro.magnet.fsu.eduusers.umassmed.edu
journalofillustratedscience.blogspot.com
Connective Tissue• Found everywhere in the body and most widely
distributed
• Functions– Connects, supports, protection, insulation, and
transportation
• Four main classes– Fibrous tissue and fat– Cartilage– Bone– Blood
Characteristics of Connective Tissue
• Common origin– All arise from mesenchyme
• Degree of vascularity– Some avascular, while others highly vascular
• Extracellular Matrix– Tissue made up mostly of matrix • Ground substance
Structural Elements of CT• Ground substance
– Interstitial fluid between the cells allows for diffusion between blood vessels and cells
– CAP, GAG, Proteoglycans
• Fibers– Provide support
• Collagen• Elastic• Reticular
• Cells– Fibroblasts, macrophages, leukocytes, plasma cells, mast cells,
adipocytes
Fibrous Connective Tissue• Loose connective tissue
– Areolar• Serves to support most epithelium• Very loose fibers run in various directions
– Reticular• Framework of “soft organs”
• Dense connective tissue– Dense regular
• Composed of closely packed parallel collagen fibers• Fibroblast only type of cell• Tendons and ligaments
– Dense Irregular• Thick collagen fibers running in various direction• Compose the dermis, and fibrous sheaths around various organs
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Fibrous Connective Tissue
• Adipose tissue– Composed of adipocytes
that store fat– Functions as insulation
and support– Most fat is white fat– Children also produce
brown fat• Heat production
carlalbert.edu
Cartilage• Supportive connective tissue with flexible
rubbery matrix
• Chondroblasts secrete matrix until they are trapped.– Chondrocytes
• Avascular– Dependent on diffusion– Slow metabolism, slow to heal
Cartilage• Three types
– Hyaline• Clear glassy matrix with collagen fiber• Found at the ends of bones, larynx, trachea, and chest• Composes fetal skeleton
– Elastic• Matrix composed of elastic fibers• Perichondrium sheath• Ear, epiglottis
– Fibrocartilage• Matrix composed of thick parallel collagen bundles• No perichondrium sheath• Pubic symphysis, intervertebral discs, menisci• Compression and shock absorption• Sometimes transition between dense connective tissue and hyaline
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dspace.udel.edu
biology.clc.uc.edu
Bone• Osseous Tissue– Spongy– Compact
• Hard calcified matrix containing collagen fibers– Deposited in concentric lamellae around central canal
• Blood vessels and nerves– Osteoblasts, osteocytes, osteoclasts
• Support, protection, movement, mineral and fat storage, blood production
technion.ac.il
Blood
• Fluid connective tissue– Formed elements in a fluid matrix (plasma)
• Transport nutrients, wastes, gases ...
• Found within blood vessels
altered-states.net
Muscle Tissue
• Highly cellular, well vascularized tissues responsible for movement
• Capable of contraction and producing tension
• Three types– Skeletal– Smooth– Cardiac
Nervous Tissue
• Main component of nervous system– Regulates and controls various functions
• Capable of transmitting electrical impulses
• Two cell types– Neurons
• Conduct impulse– Supporting cells
• Nonconducting, insulate and protect neurons
• Read the section on inflammation and repair