human anatomy i: tissues, skin & bones. some basic ideas anatomy describes the physical parts...
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Human Anatomy I:Tissues, Skin & Bones
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
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
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
Clockwise from upper left: simple columnar; simple cuboidal; stratified squamous
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
Major Organ
Systems
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
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)
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
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
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
Human skin also possesses a number of different kinds of sensory receptors (for temperature, pressure or touch, pain)
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
Above are some hydrostatic skeletons, in a roundworm and an earthworm. To the right is a shed exoskeleton of a cicada.
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
Axial skeleton
Appendicular skeleton
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 we’ll look at these with muscles
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
Long bones above, flat bones below
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
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