Tissues, organs, and organ
system
Which of the following are never
multicellular?
1.
2.
3.
4.
5.
Fungi
Animals
Plants
Bacteria
All can be multicellular
Outline
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•
•
•
•
Stem cells
Kinds of Tissues
Organs
Organ systems
Homeostasis
All human life begins with a single cell
All the cells of your body come from
that single cell
• The process by which
one cell becomes many
kinds of cells is called
differentiation
• There are
approximately 200 cell
types in the human
body
• And 100 trillion cells
Cell differentiation becomes more and
more specific during development
• Cells which can
differentiate into any
kind of cell are called
totipotent
• Cells which can
differentiate into more
than one cell are called
pluripotent
Cells differentiate according to signals
from their neighbors
• One of the major
promises of stem cells
comes from this fact
• Stem cells can thus be
used to heal damaged
tissue, such as nervous
tissue, cardiac tissue, or
bone marrow
Tissues
Groups of similar cells working
toward a common task
There are four major types of human
tissue
•
•
•
•
Epithelial
Connective
Muscle
Nervous
Epithelial tissue forms body surfaces
and lines body cavities
•
•
•
•
Squamous tissue- flat, easily passed
Cuboidal- cube-shaped, often secretory
Columnar- Oblong, often formed in glands
Ciliated- featuring cilia
Epithelial tissue is bound to connective
tissues by a basement membrane
• Basement membrane- acellular surface made of
proteins and polysaccharides
• Usually connects epithelia to loose connective tissue
Epithelial cells can form glands
• A gland- a
collection of cells
which secrete a
product
• Exocrine- release
substances through
ducts or tubes
Endocrine glands secrete hormones
directly into the body
• Hormone- a signalling
chemical which is
released in one part of
the body and affects
another part of the
body
• Examples- Insulin,
Follicle stimulating
hormone, testosterone
Connective tissues are diverse in
structure
• They include bone,
cartilage, adipose tissue
(fat cells), blood, etc.
• Most connective tissue
exists in an extracellular
matrix
• Fibers add flexibility,
durability, and strength
Collagen adds tensile strength, elastin
flexibility
The extracellular matrix often determines
the properties of connective tissues
• Fibrous connective
tissues
• Loose• Dense
• Elastic
Adipocytes have
very little
extracellular
matrix
• Sits beneath skin
• Provides insulation,
energy storage
• Also protects organs
Bone is a kind of connective tissue
• Osteocytes are
surrouned by a matrix
rich in collagen and
calcium
• Chondrocytes of
cartilage
• Blood is also a tissue
Muscle tissue
• Contractile tissue
• For movement of
body, blood,
organs
• Three major kinds
– Smooth
– Skeletal
– Cardiac
• All contain actin
and myosin fibers
for contraction
Smooth muscle
• Involuntary muscle
• Forms contractile
linings of organs and
blood vessels
• Found in digestive
system, e. g. esophagus
Skeletal muscle
• Mounted on bones for
body movement
• Striated
• Mostly voluntary
(sometimes involuntary,
e. g. reflexes)
• Individual muscles
wrapped in connective
tissue sheath
Cardiac muscle
• Involuntary muscle of
the heart
• Cells communicate with
each other closely to
allow simultaneous
contraction
• Irregular striations
Skeletal, cardiac muscle striations
are bands of actin and myosin
Neurons carry messages
• Neurons are the basic
unit of the nervous
system
• Many connections are
the cause of brain’s
complexity
• Length increases speed
and fidelity of
communication
• Neurons communicate
with electrochemical
signals
Generalized neuron structure
Glial cells provide support
• Schwann cells provide
protection, electric
insulation
• Astrocytes provide
nutrition
The cells in tissues are held together with
transmembrane proteins
• Tight junctions- ensures
passage of substances
through cells
• Adhering junctions
allow stretching
• Gap junctions- allow
cell-to-cell
communication
between adjacent cells
in a tissues
Protein junctions bind membrane
layers to a basement membrane
• Tight junctions usually sit
higher- prevent leakage
• Adherens band form a ring
around epidermal cells in
membrane
• Hemidesmosomes bind
epithelial cells to basement
membrane
• Gap junctions allow
communication between
cells
Membranes cover and protect
organs and other surfaces
• Two major kinds of
membranes:
– Epithelial
– Connective tissue
• Two major kinds of
epithelial membranes:
– Mucous: contain glands
to secrete substances
– Serous: secrete only
serous fluid
Fig. 4.7, p. 75
When a fertilized egg begins to divide,
which cells form first?
1.
2.
3.
4.
5.
bone marrow
Adipose
stem cells
neural
heart
20%
1
20%
20%
2
3
20%
4
20%
5
Muscle that is NOT striped and is
involuntary is
1.
2.
3.
4.
5.
cardiac.
20%
skeletal.
striated.
smooth.
both cardiac and smooth.
1
20%
20%
2
3
20%
4
20%
5
Organs
• Collections of tissue
which form functions
together
• Heart, kidney, etc.
• Contained in body
cavities– Cranial/spinal
– Thoracic
– Abdominal/pelvic
The heart is an organ
• Main tissue: the tissue
forming the greatest
mass of the organ
• Heart: cardiac muscle
• Sporadic tissues: tissues
comprising a minority
of the mass of the
organ
• Nervous tissue,
connective tissue
(blood vessels, etc.)
SUPERIOR (of two body parts, the one closer to head)
distal (farthest from trunk or
from point of origin of a body
part)
frontal plane
(aqua)
midsagittal
plane
(green)
proximal (closest to
trunk or to point of
origin of a body part)
ANTERIOR
(at or near front of body)
POSTERIOR
(at or near back of body)
Fig. 4.8b, p. 76
INFERIOR
(of two body parts,
the one farthest from head)
transverse
plane
(yellow)
Organ Systems work together
toward collections of general tasks
Fig. 4.9, p. 77
Lymphatic
System
Respiratory
System
Digestive
System
Urinary
System
Reproductive
System
The integumentary system includes
the body’s largest organ, the skin
• Many kinds of
tissue, each
comprised of many
kinds of cells
• Smooth muscle- for
contraction
• Adipose cellsconnective tissue
• Sweat/sebaceous
glands (endocrine
or exocrine?)
Functions of the skin
• Protect body from
foreign invaders
• Protect against
• Detect environmental
information
• Regulate temperature
• Synthesize vitamin D
There are 3 basic layers to the skin
• Epidermis, dermis, and
hypodermis
• Epidermis- source of
structures such as hair
follicles,
sweat/sebaceous glands
• Made mostly of
keratinocytes,
• Melanocytes give skin
its color
There are 5 basic layers to
epidermis
• Corneum, lucidum, granulosum,
spinosum, and basale
• Corneum stratum:
– stratified sqamous epithelium
– empty, dead cells
• Lucidum- Only in callous forming
regions
• Spinosum- cells are keratinized
• Basale- source of “Epidermal
stem cells”
There are 3 basic layers to the skin
• Dermis
–
–
–
–
–
mostly loose connective tissue
Provides flexibility
Vascularized
Nerve endings terminate
Separation of dermis from
epidermis causes a blister
• Hypodermis/subcutis:
– Fatty tissue (50% of body)
– Connects skin to bone or
muscle
One cm2 has:
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•
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200 nerve endings
100 sweat glands
10 hairs with muscles
15 oil glands
12 heat receptors
25 pressure receptors
2 cold receptors
3 blood vessels
Activity-Determine the resolving power of
skin
• Procedure
1. Prepare 4 tape-bound pin pairs, d = .3cm, .5cm,
1.0cm, 1.5cm
2. Determine resolution at ~high fidelity (.8 or
better) for: fingertips, back of hand, forearm,
back of neck
3. Record data
4. Present results
5. Interpret results
Epidermal/dermal layers in closeup
Which of the following statements is false
concerning the outermost layer of the
epidermis?
1.
2.
3.
4.
5.
It is the first to experience any abrasion.
Keratin provides waterproofing.
Millions of cells are worn off daily.
Its cells are undergoing rapid cell division.
It is called the stratum corneum.
Homeostasis
Homeostasis means “staying the
same”
• Recall: Living
things do not exist
at equilibrium
• Living things do
exist at “steady
state”
• Living things work
to maintain a
stable internal
environment
A closed system
eventually reaches
equilibrium
G < 0
A closed hydroelectric system
G = 0
The body works to maintain a constant,
stable internal environment
• This requires changes to
account for an unstable
external environment
• Homeostatic
mechanisms exist
throughout the body
• Temperature, blood pH,
dO2, [glucose], etc. are
all regulated by
negative feedback
A thermostat operates by negative
feedback
• The classic homeostatic
mechanism analogy
• How does it work?
• What mechanisms must
it contain in order to
function properly?
• What is its cost?
hormonal signals from
“thermostat” centers in
hypothalamus
motor
neurons
skeletal
muscles
smooth muscles in
arterioles in skin
sweat glands
voluntary
changes in
behavior
muscle
tone,
shivering
vasoconstriction,
vasodilation
sweating
adjustments
in heat gain
or heat loss
adjustments in
muscle activity
(in metabolic
heat output)
adjustment in
loss or
conservation of
metabolic heat
adjustment
in heat loss
Fig. 4.14c, p. 82
The price of minimizing entropy is the
constant expenditure of free energy
Why do you think homeostasis
with respect to temperature and
pH might be important?
Think of mechanisms and structures
which might depend on a stable
internal environment.
A few human body mechanisms
operate on positive feedback
• Some are regulated by
positive feedback
Other Positive feedback
mechanisms in real life
More positive feeback loops
A large increase in the body’s core temperature
will cause what change in proteins?
1.
2.
3.
4.
5.
Denaturation
an increase in function
Replication
doubling of the rate of a reaction
a small reduction in the rate of reaction
Which of the following involves a
positive feedback mechanism?
1.
2.
3.
4.
5.
temperature control
childbirth
glucose concentration
absorption of toxins
muscle concentration