Transcript Four Tissue Types

Lecture 5 Tissues
Histology
• How we examine tissues:
Teased, smeared or squashed samples, scraped – we
are looking at whole cells
Thin sections – very thin sections of the tissue are
made using a microtome after tissue has been
either frozen or embedded in some sort of solid
substance like wax or plastic –
Staining – In either case stains are used so enhance
contrast in the specimen
• What you need to know about tissues
• Appearance – be able to identify from photograph
or possibly microscope slide
• Where it might be found – specific example
• Kinds of cells involved
• Other details as cell types present, cilia, microvilli,
etc. – see histology handout
Four Tissue Types
• Tissue – group of similarly specialized
cells performing a similar function.
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Epithelial
Muscle
Connective
Nervous
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Epithelial Tissue
Functions: protection, absorption,
secretion
Cover all virtually all body surfaces, in
and out
Lack vascular supply
Classified based on shape and stacking
of cells
Generally supported on a basement
membrane (& connective tissue)
Classification of epithelial tissues
1) Cell shape (at free surface)
a) squamous - flat cells
b) cuboidal - cube shaped
c) columnar - column shaped
Reminders: -histology = thin section of a 3D object
-there are MANY tissues on each slide
Classification of epithelial tissues
2) Cell layers/arrangement
a) simple - a single layer
- relatively thin/fragile
- found lining internal structures
- simple squamous epithelium pictured
here
b) stratified
w/out
-multiple layers
-thicker
-may be in areas w/ stress
-stratified squamous epithelium
keratin pictured here
Name this epithelial tissue:
Cell arrangement/layers…….Shape of cells at surface
Name this epithelial tissue:
Pseudostratified Columnar (Fig 3.6.b):
-Lining much of the respiratory tract
-often have cilia & goblet cells
-looks layered BUT there is really only 1 layer of cells with nuclei at
different heights
Name this epithelial tissue:
Cell arrangement/layers…….Shape of cells at surface
Name this epithelial tissue:
Figure 3.6b
• Glands
• Two types: How do they differ?
– Endocrine
– Exocrine
• Classification of exocrine glands
– Means of secretion
• Merocrine
• Apocrine
• Holocrine
– Complexity of structure
Connective Tissue
• Most abundant tissue in body
• Not on free surfaces
• Cells separated in a matrix (ground substance +
fibers)
• Good nerve & blood supply (except cartilage &
tendons- dense connective)
• Classified based on matrix components,
arrangement and type of protein fibers
Connective Tissues
Connective
Tissue
Proper
Loose
Dense
Fluid
Connective
Tissue
Blood
Lymph
Support
Connective
Tissue
Cartilage
Bone
Connective Tissue Proper – Loose
• Areolar:
– Highly vascular
– Semi-liquid ground substance
– Cushions, subcutaneous, deep to digestive,
respiratory, etc.
• Adipose
– As areolar, but more adipocytes
– Cushions, energy storage
• Reticular
– Reticular fibers, macrophages, fibroblasts
– Stroma of liver, spleen, lymph nodes, bone
marrow
Connective Tissue Proper: Loose
Connective Tissue
Adipose and Adipocytes
– Develop from areolar connective – ‘on demand’
– Metabolically active
– May ‘deflate’ but do not go away
– Store lipids as energy reserve
Dense Connective Tissue
• High concentration of collagenous fibers
• Two types:
– Dense regular
• Tendons – muscle to bone
• Aponeuroses – broad sheets
• Elastic tissue – resilience – walls of blood
vessels
• Ligaments – bone to bone
– Dense Irregular
• Reinforcement of skin, capsules surrounding
internal organs, cavities of joints
Cartilage – 3 types
• Hyaline – ends of ribs, synovial joint surfaces,
fetal skeleton
– Stiff, flexible
• Elastic – examples: ear, epiglottis
– Resiliant and flexible
• Fibrocartilage – in knee joint, pubic sympysis,
intervetrebral discs, involved in bone repair
– Resists compression, provides some flexibility
in joint
Hyaline Cartilage
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Bluish-shiny white rubbery substance
Chondrocytes sit in spaces called lacunae
No blood vessels or nerves so repair is very slow
Reduces friction at joints as articular cartilage
Fibrocartilage
• Many more collagen fibers causes rigidity & stiffness
• Strongest type of cartilage (intervertebral discs)
Elastic Cartilage
• Elastic fibers help maintain shape after deformations
• Ear, nose, vocal cartilages
Muscle
further discussion in later sections
• Specialized cells containing myosin and actin
(protein) fibers which produce contractions or
movement
• Types:
• Smooth – involuntary – lack striations
----Two types with striations----------• Skeletal – voluntary muscle; have cross striations
and responsible for body movement
• Cardiac – only found in heart – branched cells
bound end to end by intercalated discs
Nervous Tissue
• Involved in sensing and conducting and analysis of
information
• Two cell classes:
• Neurons – which conduct impulses
• Neuroglia – which support neurons by providing
support, protection and nourishment
• Further Discussion with nervous system