Human Anatomy I: Tissues, Skin

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Human Anatomy ITissues, Skin Bones
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Some Basic Ideas

• Anatomy describes the physical parts of an
  organism
• Physiology describes the way in which those parts
  work, alone and in combination
• Most organisms are organized into different
  levels
• Cells
• Tissues groups of cells performing some specific
  function
• Organs groups of tissues performing some
  specific function
• Organ systems groups of organs performing some
  specific function

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Tissue Types

• There are 4 main kinds of tissues
• Epithelial Tissue
• Connective Tissue
• Muscle Tissue
• Nerve Tissue
• Most organs are a combination of two or more
  tissues

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Epithelial Tissue

• Serves as covering or lining of various body
  parts
• Involved in both absorption of material and
  secretion of material
• Cells can vary in shape
• Squamous cells are flat found in areas where
  diffusion important
• Cuboidal cells are cubes involved in secretion
  and absorption
• Columnar cells are rectangular also used for
  secretion and absorption
• Tissue can vary in of layers
• Simple epithelium has one layer
• Stratified epithelium has 2 or more can be
  different cell types

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Clockwise from upper left simple columnar
simple cuboidal stratified squamous
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Connective Tissues

• Perform a variety of functions
• All consist of two components
• Living cells, scattered in a
• Non-living matrix secreted by these cells
• Some examples include
• Bones
• Cartilage
• Adipose (fatty) tissue
• Blood
• Ligaments
• tendons

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Major Organ Systems
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Integumentary System

• Or, more commonly, skin!
• Major functions include
• A barrier to injury or invasion by other
  organisms
• A (very large) sensory organ
• Production of body covering (hair, scales,
  feathers)
• Production of various substances (toxins,
  pheromones, lubricants, etc.)
• Body cooling (via sweat)
• Assistance with respiration

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General Anatomy of the Skin I

• Outermost layer is the epidermis
• Living epithelial cells towards interior
• Outer layer of dead cells, many filled with
  keratin (helps prevent water loss)

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General Anatomy of the Skin II

• Middle layer is the dermis
• Contains primarily connective tissue, plus
  nerves, blood vessels, muscles, sensory organs
• Hairs and glands appear to come from this region,
  but actually are infoldings of the epidermis

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General Anatomy of the Skin III

• Inner layer is the hypodermis, or subcutaneous
  layer
• Mostly a layer of adipose tissue, which helps
• Cushion underlying organs
• In heat retention
• Also contains some nerves and blood vessels

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2 Primary Skin Glands in Humans

• Sweat Glands, with two types
• Eccrine sweat glands occur over most of body
• Release a clear fluid, mostly water with
  dissolved salts
• Apocrine sweat glands are found mostly in groin,
  armpits, face
• Release more viscous and odor-causing fluid
• Sebaceous Glands
• Release a thicker, oily/waxy fluid called sebum
• Helps lubricate hair follicles

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Human skin also possesses a number of different
kinds of sensory receptors (for temperature,
pressure or touch, pain)
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Skeletal System

• Major functions include
• Protection for internal organs
• Attachment points for muscles
• Some animals possess a hydrostatic skeleton
• Body is a fluid-filled bag under pressure which
  animal can push against
• Others have an external skeleton, or exoskeleton
• Still others possess an internal skeleton

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Above are some hydrostatic skeletons, in a
roundworm and an earthworm. To the right is a
shed exoskeleton of a cicada.
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Anatomy of the Human Skeleton

• The axial skeleton consists of bones along the
  midline of the body
• Includes skull, spinal column, ribcage, sternum
• The appendicular skeleton is everything else
• Includes arm bones, leg bones, pelvic girdle,
  pectoral (shoulder) girdle

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Axial skeleton
Appendicular skeleton
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3 Components of Skeleton

• Bones the hardest part of the skeleton
• Cartilage more flexible than bone
• Ligaments a type of connective tissue linking
  two bones
• NOTE tendons link muscles to bones, but well
  look at these with muscles

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Bone Structure

• Bones may be long, short, flat, or irregular in
  shape
• Most bones have a dense region of compact bone,
  and a less dense region of spongy (or cancellous)
  bone
• Within the spongy bone of long and flat bones is
  red marrow
• Involved in production of red blood cells
• Within the shaft region of long bones is yellow
  marrow
• Mostly fat storage
• Can be converted to red marrow in emergencies

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Long bones above, flat bones below
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The Inside of Bones

• The living cells in bones are called osteocytes
• Osteocytes are found within spaces called lacunae
• Osteocytes produce bone, which is the non-living
  matrix part
• Osteocytes are arranged (at least in compact
  bone) in groups called osteons, or a Haversian
  system
• In the middle of each osteon is a canal
  containing blood vessels to nourish the osteocytes

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Joints

• Joints occur where two bones come into contact
  and can move relative to each other
• At the end of each bone is a layer of cartilage
• Ligaments link bones
• Fluid usually fills space between bones to reduce
  friction and wear