Animal Structure and Function

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Animal Structure and Function

• JP Slovak
• Texas AM University-Commerce

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Epithelial tissues

• Covers organs, covers inner lining of body
  cavities and line hollow organs
• basement membrane - nonliving layer connected to
  connective tissue
• lack capillaries
• cells reproduce readily
• cells are tightly packed and held together by
  desmosomes

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Classification of tissues

• Simple squamous
• single layer of thin flattened cells
• highly permeable
• line alveoli of lungs and forms capillaries
• Simple cuboidal
• single layer of cube shaped cells
• covers ovaries and line ducts of certain glands

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Classification

• Simple Columnar
• elongated
• nuclei located near basement membrane
• line uterus stomach and intestines
• thick and able to protect underlying tissues
• secretes digestive fluids
• absorbs nutrients
• microvilli and goblet cells(secrete mucus)

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Classification

• Pseudostratified Columnar
• appear layered
• cell nuclei are at two levels
• cells vary in shape but all reach basement mem
• often have cilia
• goblet cells secrete mucus, cilia sweep
• line respiratory and reproductive passages

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Classification

• Stratified squamous
• outermost layers are squamous
• relatively thick tissue
• deeper layers are columnar or cuboidal
• as cells move outward they become flattened
• epidermis
• older cells acquire keratin
• lines oral cavity, throat, vagina, and anal canal
• is not keratinized in these parts

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Classification

• Stratified cuboidal
• two or three layers which provide protection
• lines mammary,sweat and salivary glands
• Stratified columnar
• outside cells elongated
• lower layers are cuboidal

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Classification

• Transitional epithelium
• changes in response to tension
• inner lining of bladder and ureters
• during contraction of these organs the layers are
  cuboidal in shape
• when distended, appears to contain only a few
  layers of cells

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Classification

• Glandular
• specialized to secrete substances into ducts or
  body fluids
• endocrine
• exocrine
• merocrine
• apocrine
• holocrine

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Connective Tissue

• Most abundant tissue
• bind
• provide support
• store fat
• have a matrix - has fibers and a ground substance
• cells do reproduce
• vascularity varies

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Cell types

• Fibroblast
• most common
• large and star shaped
• produce fibers by secreting proteins into matrix
• Macrophages
• originate as wbc
• almost as numerous as fibroblasts
• Mast cells
• located near blood vessels
• release heparin and histamine

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Connective Tissue fibers

• Collagenous fibers
• made of the protein collagen
• flexible, but have great tensile strength
• if abundant collagen fibers (dense connective)
• Elastic fibers
• microfibrils embedded in elastin
• easily stretched or deformed
• vocal cords and air passages
• Reticular fibers - thin collagenous fibers which
  are highly branched

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Adipose Tissue

• Fat
• accumulate fat over time
• tissue is found in various sites
• helps cushion joints and some organs
• a person is born with certain of fat cells

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Dense Connective tissue

• Has many closely packed collagenous fibers
• few fibroblasts
• very strong
• helps bind body parts together (tendons)
• poor blood supply

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Cartilage

• Provides structural support
• matrix is abundant
• ground substance is rich in protein-polysaccaride
  complexes
• perichrondrium - outer covering with blood supply
• Hyaline,elastic, and fibrocartilage

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Bone

• Most rigid connective tissue
• calcium phosphate and calcium carbonate
• provides support and protection
• osteocytes and lamella
• haversian canals
• osteon ( Haversian system)
• canaliculi

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Blood

• Cells are suspended in fluid(plasma)
• red and white blood cells and platelets
• most bc formed in red marrow of hollow bones
• only rbc function entirely in vessels

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Muscle tissue

• Contractile tissue
• Skeletal - voluntary
• smooth - lack striations. Found in different
  organs
• Cardiac - found only in the heart
• intercalated disk

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Nervous tissue

• Found in brain, spinal cord and peripheral nerves
• neurons
• neuroglial cells