Body Organization and
Homeostasis
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Organization
of the Human Body…
…increases in complexity from cells to organ systems
„ Multi-celled organisms require specialized cells to perform
specific tasks
„ Specialized cells are organized from
Four Type of Tissues
Introduction to Organs and Organ Systems
Body Cavities and Anatomical Terms
Integumentary System
Homeostasis
Cells
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Organ
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Organ systems
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Tissues are…
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Epithelial - covers body surfaces, lines cavities and tubes, and forms
glands
Connective - binds and supports body parts, serves as a storage site
for fat, and plays an important role in immunity
Muscle – an excitable tissue that is responsible for the movement of
the organism and the substances through the organism
Nervous-an excitable tissue that receives stimuli and conducts nerve
impulses
Organs
Organ Systems
A group of cells of similar type that work together to serve a
common function
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… groups of cells that have the same structural characteristics
and perform a common function
„ Histology is the study of tissues
„ There are four major types of tissues in the body
Tissues
Tissue
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Structures composed of two or more tissue types joined together
that perform a specific function or functions
Groups of organs that together serve a broad function such as
protection, movement, excretion of wastes
Epithelial Tissue
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Groups of cells that form a tight, continuous network
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Cells are anchored by a basement membrane on one side and free on
the other side
Named after the appearance of cell layers and the shape of the cells
Locations
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Functions
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Glandular epithelia are specialized epithelium that secrete a product
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Lines body cavities and tubes, covers body surfaces, and is found in glands
Mouth, skin, inner surface of the digestive tract, kidney tubules, lungs,
bladder, and blood vessels
Protect underlying tissues, absorb nutrients, secrete wastes
Exocrine glandular epithelia – secrete a product into a hollow organ or duct
Endocrine glandular epithelia – secrete a product (hormones) into the
intercellular spaces and which then diffuse into the blood stream
There is transitional epithelium that changes in appearance in response
to tension - urinary bladder
How Epithelia Tissues are Named
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Number of cell layers
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Simple- one layer of cells
Stratified- more than one layer of cells
Pseudostratified- appears to have layers
but only has one layer
Shape of cell
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Cuboidal- cube- shaped
Columnar- column
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Squamous- flattened
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Pseudostratified ciliated columnar epithelium
•Columnar shape and appears to be layered
•Located in the linings of the respiratory tract and reproductive system tubes
•Functions include protection, secretion, movement of mucus and of sperm
and egg (via cilia)
Basement Membrane
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Functions as mortar to anchor cells and
provides structural support
Comprised mostly of protein secreted by
epithelial cells
Do not confuse with plasma membrane
which is a part of every living cell
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Functions
of Connective Tissue
Connective Tissue
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It is the most abundant and widely distributed tissue in the body
All have specialized cells embedded within an extracellular matrix
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Bone = solid, cartilage = gelatinous, blood = fluid
Generally secreted by the cells within the matrix
Binds, supports, and protects parts of the body
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Wraps, cushions, and insulates organs
Stores fat
Produces blood cells and acts as a transport
medium
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Fibers - produced by fibroblasts
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Ground substance is non-cellular and ranges from solid to fluid
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Collagen - contain collagen, a protein that gives flexibility and strength
Elastic - contain elastin that can stretch and recoil like a spring
Reticular - thin strands of collagen that branch extensively forming
interconnecting networks
The body’s glue
Consists mostly of matrix not cells
Grouped into two broad categories
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Connective tissue proper - loose (areolar and adipose) and dense
Specialized connective tissue - cartilage, bone, and blood
Specialized Connective Tissue:
Cartilage
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Matrix is solid but flexible
Cells are in chambers called lacunae
Does not contain blood vessels
3 types are distinguished by types of fibers
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Hyaline cartilage – fine collagen fibers
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Elastic cartilage – more elastic fibers than collagen fibers
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Fibrocartilage – strong collagen fibers
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Location: Nose, ends of long bones, fetal skeleton, rings of trachea…
Location: Outer ear
Location: Disks between vertebrae
Functions
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Transition tissue from which bone develops
Maintains shape of certain body parts
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Ex tip of nose, outer ear
Disks of cartilage separate and cushion vertebrae
Reduce friction in some body joints
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•Contains few living cells
•Consists mostly of matrix of hard of mineral deposits
•Contains blood vessels so can heal quickly
•Stores minerals and lipids and produces blood cells
• Consists of cells suspended
in fluid matrix called plasma
• Derives from stem cells in
bone
• Type of blood cells
– RBC transport O2 and nutrients
and carry away waste products
of metabolism
– WBC defend body again
disease
• Congregate in fluid matrix
called lymph
– Platelets participate in blood
clotting
Muscle Tissue
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Consist of muscle cells AKA muscle fibers
Specialized to shorten or contract resulting in
movement
Long, thin, and aligned parallel to each other
Three types
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Skeletal, cardiac, and smooth
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Nervous Tissue
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Two major cell types
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Neurons specialized for generating and
transmitting electrical impulses
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Neurons or nerve cells
Neuroglia or glial cells
Allows for communication between cells through
sensory input, integration of info, and motor output
Located in brain, spinal cord, nerves
Junctions Between Cells
• Parts of neuron
– Cell body with nucleus,
dendrites, axon
– Can be long
• Glial cells
– Surround, protect, and
supply nutrients to
neurons
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Tight junctions- seal the plasma membranes of
adjacent cells so nothing can pass between them
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Cells of digestive tract, kidney tubules, blood brain
barrier
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Adhesion junctions- sometimes called
desmosomes allow some movement between so
tissues can stretch and bend
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Gap junctions- connection channels that permit
movement of ions or water between cells
– Outnumber neurons 9:1
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Epithelial cells of skin
Muscle cells and some epithelial cells
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Organs and Organ Systems
Perform Complex Functions
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Organs are structures composed of two or
more tissue types joined together that
perform a specific function or functions
Organ systems are groups of organs that
together serve a broad function such as
protection, movement, excretion of wastes
Body Cavities
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Ventral or anterior cavity
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Thoracic cavity-lungs and heart
Abdominal cavity
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Thoracic and abdominal
Upper: stomach, liver, spleen, small
and some of the large intestine,
Lower: rectum, bladder, reproductive
organs, rest of the large intestine
Dorsal or posterior cavity
Cranial cavity - brain
Spinal cavity (AKA) vertebral canal spinal cord
Pelvic cavity
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Body Membranes
Describing Body Position or Direction
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Body cavities and organ surfaces are covered with membranes
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Mucus membranes line passageways that open to the exterior of
the body
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Some secrete mucus that trap bacteria and viruses
Serous membranes line the thoracic and abdominal cavities and
their organs
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Secretes watery fluid to lubricate the organs within
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Pleura: lungs, Peritoneum: abdominal organs, Pericardium: heart
Synovial membranes line cavities of freely movable joints
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Secrete synovial fluid into joint cavity to lubricates
Cutaneous membrane or skin is thick, waterproof, and dry
Meninges
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Serve as a protective covering of the brain and spinal cord
Meningitis is a life-threatening infection of the meninges
Anatomical position face and palms forward
Integumentary System
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Includes the skin and accessory organs such as hair, nails, and glands
Skin is <1/4 inch thick yet it one of the largest organs
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1/12 of body weight and surface area of 1.8 to 2.4 yd2
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Functions
„ Protects the body from physical trauma, invasion by pathogens, and
water loss
„ Helps regulate body temperature
„ Allows us to be aware of our surroundings through sensory receptors
„ Synthesizes chemicals such as melanin and vitamin D
„ Excretes some metabolic wastes
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Outermost layer of the skin consisting of stratified squamous epithelium
Constantly being replaced
Two dominant cell types
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Keratinocytes produce keratin, a waterproof protein
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Melanocytes produce melanin which protect against UV rays and gives skin its
color
„ Humans have same # of melanocytes but differ in the form of melanin
produced and the size and number of pigment granules
„ Vitiligo - melanocytes disappear from certain parts of body and leave white
patches
„ Albinism - melanocytes can’t produce melanin and person lacks pigments
in the eyes, hair and skin
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Cells in the uppermost layer are dead and become filled with keratin thus
acting as a waterproof barrier
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Dead due to distance from blood supply
Some cells convert cholesterol to inactive form of vitamin D
Two Regions of the Skin
Contains elastic and collagen fibers that provide strength
and elasticity
Skin becomes less flexible and more wrinkled with age
since the numbers of fibers decreases
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Anterior or ventral - at or near
the front
Posterior or dorsal - at or near
the back
Superior/Inferior - situated
above/below
Proximal/distal - closer/further
in proximity
Medial/lateral - toward/away
midline
The thick, inner layer of the skin
Made of dense fibrous connective tissue
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Liposuction
Dermis
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Two principal layers called the epidermis and the dermis
Hypodermis or subcutaneous layer is a layer beneath the skin between the
dermis and internal structures where fat is stored
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Midsagittal/sagittal - left and right
Frontal - front and back
Transverse - top and bottom
Epidermis
Structure
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Planes that divide the body
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Usually composed of sheets of epithelium supported by connective
tissue
Also influenced by sun and smoking
Contains sensory receptors, blood vessel, hair, and
glands
Does not wear away like the epidermis
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Explains durability of tattoos (droplets of ink)
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Skins Accessory Organs:
Hair and Nails
Skin Accessory Organs: Glands
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Hair
Filament of dead keratinized skin cells formed into a
column
Functions include protection from debris, heat retention
and sensation
Consist of a shaft, root, and follicle at base
Small smooth muscle contracts when we are frightened or
cold and hair becomes erect - Arrector pili muscle
Color is the result of different types of melanin molecules
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Sebaceous or oil glands secrete oily fluid that moistens and
softens hair and skin
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Sweat glands produce sweat or perspiration
„ Watery fluid containing ions, small amounts of metabolic wastes,
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Nails are also dead cells designed to protect the tips
of our toes and fingers
Found in proximity of a hair follicle
Found all over the body except the palms of the hands and soles
of the feet
Acne - active infection of blocked oil gland NOT due to eating
french fries, chocolate, or stress
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and an antiobiotic peptide called dermicidin
Helps regulate body temperature and protects against bacteria
Most numerous glands in the skin
Wax glands are modified sweat glands found in the external ear
canal that protect against dehydration and injury
Skin Cancer
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Basal cell carcinoma is the most
common yet least deadly form
Melanoma is the most deadly form
but is the least common
What can you do to help prevent
this?
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Stay out of the sun between 10am3pm
Wear protective clothing (tight
weave, treated sunglasses, widebrimmed hat)
Use sunscreen with an SPF of at
least 15 and protects from UV-A and
UV-B rays
Don’t use tanning beds
Homeostasis
Types and Differences of Burns
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Classified according to depth and severity
First degree burn is the least serious and involves only the
epidermis
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Example is mild sunburn
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Second degree burn involves the epidermis and the dermis
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Third degree burn involves damage or total destruction of the
epidermis, dermis, and subcutaneous layer
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Burn site painful, red, dry, and absent of blisters
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Burn site painful, red, and blistered with swelling
Patient feels little or no pain since nerve ending are often damaged
Maintenance of a constant internal environment that is
essential to life
Nervous and endocrine system are important in coordinating
response to a change but all body systems contribute
Body conditions are not static but fluctuate around a set
point
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Blood glucose, pH levels in blood, body temp, heart rate, blood
pressure
“Thermostat” for the body is located in the hypothalamus
Maintained by negative feedback mechanisms
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Output of the system dampens the original stimulus
Control system has 3 components
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receptor, control center, effector
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Hyperthermia,
abnormally
elevated body
temperature, and
hypothermia,
abnormally low
body
temperature, are
both lifethreatening
conditions that
result when this
mechanism fails
Positive Feedback
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A mechanism for increasing the change of the
internal environment in one direction
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Rare in nature and tend to be destabilizing
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Amplify the stimulus
All Systems are
Important in
Maintaining
Homeostasis
Can be harmful such as when a fever is too high and
continues to rise
Examples include the secretion of oxytocin during
birth to continually increase uterine contractions,
blood clotting, and stomach digestion of protein
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