Download Tissues and membranes

Tissues
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Groups of cells similar in structure and function
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Most organs contain all 4 types
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Tissue has non-living extracellular material between its
cells
The four types of tissues
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Epithelial
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Connective
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Muscle
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Nerve
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Epithelial Tissue
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Cellularity – composed almost entirely of cells; little or no
extracellular matrix
Polarity – apical and basal surfaces
Special contacts – form continuous sheets held together
by tight junctions and desmosomes
Supported by connective tissue – reticular and basal
laminae
Avascular but innervated – contains no blood vessels but
supplied by nerve fibers
Regenerative – rapidly replaces lost cells by cell division
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Key cell structures at each surface
Microvilli, Cilia,
Stereocilia
Specialized
junctions
Basement membrane Sheet between the epithelial
and connective tissue layers
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Classification of Epithelia
Number of layers
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Shape
Figure 4.1a
Epithelia: Glandular
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A gland is one or more cells that makes and secretes an
a particular product (secretion)
Two groups – endocrine and exocrine
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Endocrine glands are ductless glands that produce
hormones and secrete into the blood stream
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Exocrine glands Secrete their products onto body
surfaces (skin) or into body cavities through ducts
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Exocrine Glands
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More numerous than endocrine glands
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Examples include mucous, sweat, oil, and salivary
glands
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Exocrine glands are classified according to number of
cells:
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The only important unicellular gland is the goblet
cell that produce mucin (glycoprotein) that when
dissolved in water forms mucus.
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Multicellular exocrine glands are composed of a duct
and secretory unit
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Connective Tissue Functions
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Support – bone, cartilage, ligaments, tendons,
capsules encasing organs, organ stroma
Medium for exchange of metabolic waste,
nutrients, oxygen – between blood and many
cells.
Defense and protection – blood cells, physical
barrier.
Storage of fat.
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Structural Elements of Connective Tissue
Extracellular
matrix
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Have 3 main elements:
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Ground substance – unstructured material that
fills the space between cells
Fibers – collagen, elastic, or reticular
Cells – fibroblasts, chondroblasts, osteoblasts, and
hematopoietic stem cells
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Fibers
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Collagen –
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Built primarily from the protein collagen
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Tough fibers
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Provides high tensile strength*
Elastic
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Long fibers
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Contain the protein elastin that allows stretch and recoil.
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Found in place that need elasticity: lungs, blood vessels
Reticular
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Short branch collagenous fibers that form delicate networks
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Support soft tissue of organs (ex. Around blood vessels)
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Cells
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Fibroblasts –
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Can be found connective tissue proper.
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The most common resident cells in ordinary connective
tissue.
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Fibroblasts are responsible for secreting collagen
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Chondroblasts – cartilage
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Osteoblasts – bone
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Hematopoietic stem cells – blood
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Immune system cells - White blood cells, plasma cells,
macrophages, and mast cells
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Areolar Connective Tissue: Model
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Figure 4.8
Types of connective tissue
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membranes
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Membranes are a combination of more than one tissue
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They all are multicellular sheets composed of at least 2
primary tissue types: epithelium that is bound to an
underlying connective tissue proper.
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There are 3 types:
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cutaneous
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mucous
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serous
The synovial membrane is composed of connective
tissue only
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Epithelial Membranes:Cutaneous Membrane
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Cutaneous – skin
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Figure 4.12a
Epithelial Membranes: Mucous Membrane
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Mucous – lines body cavities
open to the exterior e.g.,
digestive and respiratory
tracts)
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Moist membranes
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Most ET are simple columnar
or stratified squamous
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The underlying CT – lamina
propria
Absorption and secretion
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Figure 4.12b
Epithelial Membranes: Serous Membranes
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Serous – moist membranes found in closed ventral body cavity
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Consists of squamous ET resting on loose CT
Serous membrane is named according to the site and organ: lungs –
pleura; heart – pericardium; abdomen - peritoneum
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Figure 4.12c