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Histology defintion
study of tissues
Tissues definition
group of cells and their products working together for a particular function
4 major tissue classes
Epithelial, connective, nervous, and muscular
Epithelial tissue definition
Tissue is composed of layers of closely spaced cells that cover organ surfaces, form glands, and serve for protection, sensation, and absorption
epithelial tissue location
Epidermis, inner lining of digestive tract, liver, and other glands
Connective tissue definition
Tissue with usually more matrix than cell volume; often specialized to support, bind, and protect organs
Connective tissue location
Tendons and ligaments, cartilage and bones, and blood
Nervous tissue definition
tissue containing excitable cells specialized for rapid transmission of coded information to other cells
Nervous tissue location
brain, spinal cord, nervers
Muscular tissue definition
Tissue composed of elongated, excitable muscle cells specialized for contraction
Muscular tissue location
skeletal muscles, heart, and walls of viscera
3 layers of tissue development
Ectoderm, mesoderm, and endoderm
Endoderm forms
lining of digestive and respiratory tracts and some glands
mesoderm forms
dermis, muscle, bone, and blood cells
Ectoderm forms
the nervous system, epidermis, neural crest cells
Characteristics of epithelial tissue
Cells closely packed with very little extracellular space
Specialized cell contact
Polarity: meaning 2 different ends
Avascular: no blood supply
High regeneration rate
Specializations
Gland defintion
A cell, tissue, or organ that makes and secretes a product
Endocrine gland definition
produces hormones and secretes into bloodstream via exocytosis
Exocrine gland definition
secretes product onto the body surface or into body cavities
Which glands have ducts?
exocrine
Which glands are highly vascular?
endocrine
Structural classification of exocrine glands
Unicellular: ex. mucous and goblet cells
Multicellular: consists of a duct and secretory unit
Duct type (2)
Simple- unbranched duct
compound- branched duct
Secretory Unit (3)
Alveolar- secretory cells form small sacs
Tubular- secretory cells form tubes
Tubuloalveolar- alveolar and tubular
How is exocrine glands classified
Based on how product is secreted
3 classifications of exocrine glands
Holocrine
Apocrine
Merocrine
Holocrine definition
whole membrane rupturing
Apocrine definition
membrane budding with vesicles
Merocrine definition
secrete their products by exocytosis as they are produced
Connective tissue function
Binds organs
supports the body
physical protection
immune protection
movement
Storage
Transport
Connective tissue characteristics
All CT arise from mesoderm
Cells widely scattered within extracellular matrix
Most of CT is non-living
Highly vascularized except for cartilage
Connective tissue components
Cells- fibroblasts and miscellaneous
Fibers- collagenous, reticular, elastic fibers
Ground substance
Ground substance + fibers
= matrix
Classification of CT 4 groups
Fibrous CT
Adipose tissue
Supportive CT
Fluid CT
2 types of fibrous ct
Loose fibrous: Areolar tissue
Loose fibrous: Reticular tissue
Characteristics of areolar tissue
produce basement membrane of epithelial tissue
surrounds blood vessels, nerves, esophagus, etc
allows blood vessels and nerves access to tissues
Characteristics of reticular tissue
Forms supportive network for lymphatic system and immune cells
Numerous leukocytes i.e. white blood cells
Lots of lymphocytes
Characteristics of dense regular CT
densely packed collagen fibers and slender fibroblast nuclei
Resists regular, predictable stress
Few blood cells; little ground substance
Characteristics of dense irregular CT
Bundles of collagen fibers but irregularly arranged
Few blood vessels; little ground substance
Location of dense regular CT
Tendons and ligaments
Location of dense irregular CT
Dermis, around cartilage and bone, around viscera
2 types of adipose tissue
White fat and brown fat
Characteristics of white fat
only fat present in adults
stores energy, thermal insulation, mechanical protection
Characteristics of brown fat
in fetuses, infants, and children
Brown because of abundant mitochondria
Generates heat
2 types of supportive CT
cartilage and bone
Characteristics of cartilage
Matrix is gel-like
Avascular
Chrondoblasts secrete matrix
Chrondoblasts mature into chrondocytes
Can withstand tension and compression
3 types of cartilage
Hyaline, elastic, fibrocartilage
Characteristics of hyaline
Ease joint movement
move vocal chords
growth zones of long bones
Characteristics of elastic
Flexible support
external ear
Characteristics of fibrocartilage
Absorbs shock
Characteristics of Bone
osseous tissue
Osteoblasts, osteoclasts, osteocytes
FlMineralized matrix
Characteristics of Blood
Plasma is the matrix
Red blood cells and white blood cells
Nervous tissue includes 2 cells
neurons and neuroglia/glial cells
Muscular tissue function
specialized to convert chemical energy (ATP) into mechanical energy (movement)
3 types of muscular tissue
skeletal, cardiac, and smooth
Characteristics of skeletal muscle
most are attached to the bone
Used in body movement
voluntary muscle movement
Nonbrancing; have striations
Characteristics of cardiac muscle
Only found in the heart
pumps blood
branching; have striations and intercalated discs
Characteristics of smooth muscle
found in walls of blood vessels and digestive tract
controls blood pressure and moves food through digestive tract
Involuntary movements
No striations
Most cells are connected by
cellular junctions
What do cellular junctions do?
Holds cells together
Controls the movement of substance between cells
Allow tissues to resist stress
Allow cells to communicate with each other
3 types of specialized junctions
Tight junctions
Desmosomes
Gap junctions
Tight junction function
Prevents materials from passing between cells
Desmosomes function
resists mechanical stress but allows materials to move between cells
Gap junction function
Allows materials to pass between cells
Unipotent definition
can only make one type of cell
Multipotent definition
can make a few types of cells
Pluripotent definition
can make any type of cell in your body
2 main mechanisms for tissue repair
Regeneration and fibrosis
Regeneration definition
Replacement of damaged cells with cells of the same type
Fibrosis definition
“Fills the gaps” with scar tissue (Fibrous CT)
Atrophy definition
shrinking of a tissue due to loss of cell and cell size
Necrosis definition
Premature, pathological tissue death due to trauma, toxins, infection, etc
Infarction definition
Sudden death of tissue due to lack of blood supply
Gangrene definition
Necrosis of tissue due to lack of blood supply
Apoptosis definition
programmed cell death