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Tissues
Tissues – group of similar cell types that
perform a common function.
The human body has four basic types of
tissue:
1. Epithelial
2. Connective
3. Muscle
4. Nervous
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Tissues – Epithelial Tissue
 Epithelium is tightly packed sheets of cells that line
organs and outer surfaces, as well as the insides of
hollow organs, vessels, and body cavities.
 Epithelia are typically anchored on one face, but
free on another
 The free side is typically exposed to the environment
of body fluids
 Can be single layer or many layers thick
 Function in protection, secretion, and absorption
 Epithelial cells are continuously sloughing off and
are replaced by cell division
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Tissues – Epithelial Tissue
 Many organs are lined with epithelial tissue
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Tissues – Connective Tissue
Connective Tissue
Loosely organized and composed of cells embedded in a
matrix
Usually binds organs or tissues to one another
Six different types:
1. Loose connective tissue
2. Adipose tissue
3. Blood
4. Fibrous connective tissue
5. Cartilage
6. Bone
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Tissues – Connective Tissue
 Loose connective tissue
 Most widespread tissue in animal body
 Matrix composed of collagen and elastin fibers
 It is called “loose” because of the fibers
that are loosely woven
together
 Binds epithelia to tissues,
pads skin, and holds
organs in place
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Tissues – Connective Tissue
 Adipose tissue
 Also called fat
 Connects skin to underlying structures, pads organs
 Used for storage of energy (fat)
 Primarily cells; small
amount of matrix
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Tissues – Connective Tissue
 Blood
 Cellular component, red blood cells, white blood
cells and platelets
 Matrix is the plasma
 Functions include
carrying oxygen and
nutrients; fighting
infection
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Tissues – Connective Tissue
 Fibrous connective tissue
 Forms tendons and ligaments
 Matrix is densely packed collagen fibers running
in parallel.
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Tissues – Connective Tissue
 Cartilage
 Cellular component  chondrocytes
 Chondrocytes secrete own matrix
 Cartilage cushions joints, forms
support for ears and nose
 Not vascularized, so takes
a long time to heal if injured
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Tissues – Connective Tissue
 Bone
 Rigid connective tissue
 Osteoblasts secrete matrix that is composed of
collagen fibers and calcium salts
 Osteocytes maintain the hardened bone matrix
 Body can make use of
calcium from bones if
dietary levels are too low
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Tissues - Muscle Tissue
Muscle Tissue
Muscle is contractile tissue (capable of
shortening)
 Long, thin cylindrical cells called muscle fibers
 Two proteins – actin and myosin – interact
to cause contraction of muscle fibers
 Three types of muscle:
1. Skeletal
2. Cardiac
3. Smooth
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Tissues – Muscle Tissue
 Skeletal Muscle
 Usually attached to bone
 Produces all voluntary movements
 Striated
 Long, thin, cylindrical shape
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Tissues – Muscle Tissue
 Cardiac muscle
 Only found in heart tissue, undergoes rhythmic
contractions to produce heartbeat
 Striated and involuntary
 Branched, interlocking cells
propagate signal to
contract almost
simultaneously
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Tissues – Muscle Tissue
 Smooth muscle
 Not striated and involuntary
 Musculature of organs, blood
vessels, digestive tract
 Contracts more slowly and
for longer than skeletal muscle
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Tissues – Nervous Tissue
 Neurons conduct electrical signals and compose
the cells of the brain and spinal cord
 Main functions of neurons are to:
1. Sense stimuli
2. Process stimuli
3. Transmit signals
 Most cells of nervous system do not undergo cell
division
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Tissues – Nervous Tissue
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Tissues – Tissue Donation
 One person’s tissues can improve the lives of as
many as 50 people.
 Injuries from motor vehicle accidents, burst blood
vessels, and drowning are common causes of brain
death.
 Once dead, brain cells cannot recover.
 Brain dead is different than being in a coma or
vegetative state.
 Tissues can be treated to remove any proteins that
a person’s immune system may react to so there is
no need for donor matching.
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Organs and Organ Systems
 Organs are composed of two or
more tissue types
 Organs that act together from an
organ system
 All the organ systems of a body
form an organism
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Organs and Organ Systems – The Liver as a Model
Organ
 The liver sits below the diaphragm, is comprised of
four lobes, and is associated with the gall bladder.
 The lobes are subdivided into lobules which each
contain a central vein and hepatocytes.
 The central vein allows blood to circulate through
all of the liver.
Gallbladder
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Organs and Organ Systems - The Liver as a Model
Organ
The liver is an important component of the
digestive and the circulatory system
 As part of the circulatory system, the liver:
1.
Synthesizes blood clotting factors
2.
Detoxifies
3.
Regulates blood volume
4.
Destroys old red blood cells
 As part of the digestive system, the liver:
1.
Produces bile
2.
Metabolizes and stores nutrients
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Organs and Organ Systems – The Liver as a Model
Organ
 Liver transplants can be made from living donors
or from brain dead ones
 Unlike many organs, liver can regenerate itself
 Portion can be taken from living donor and
implanted in patient
 Liver in donor and patient will regrow to normal size
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Organs and Organ Systems – The Digestive System
 The digestive system’s role in the body is to
chemically and mechanically break down food into
nutrients which then can be absorbed.
 This process starts in the oral cavity with the teeth
performing mechanical digestion.
 Salivary amylase performs chemical digestion in
the oral cavity.
 The tongue helps you taste food and to form a
bolus.
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Organs and Organ Systems - The Digestive System
Alimentary canal
1
PLAY
2
Accessory organs
of the digestive
system
Liver
• Produces bile
which aids absorption
of fats
3
4
Gall bladder
• Stores bile and empties
into small intestine
Pancreas
• Produces digestive
enzymes
Produces a buffer
that neutralizes
acidity of stomach
acid
5
6
Mouth
• Teeth reduce the size of food, increasing
surface area available for digestion by enzymes.
• Enzymes in saliva then start breaking down
carbohydrates.
Pharynx
• Epiglottis blocks the opening to the windpipe
when we swallow, so that our food goes into our
esophagus rather than our lungs.
Esophagus
• The esophagus transports food to stomach by rhythmic
waves of muscle contractions called peristalsis.
Stomach
• Acidic gastric juices start breaking down foods.
• The enzyme pepsin breaks down proteins.
• Mucous prevents gastric juices from digesting
stomach.
• Pyloric sphincter regulates movement of
food from stomach to small intestine.
Small intestine
• Most digestion of carbohydrates, proteins, and
fats occurs here.
• Nutrients are absorbed into the bloodstream.
Large intestine
• Water is reabsorbed.
7 Anus
• Undigested materials are excreted as feces.
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Figure 16.8
Organs and Organ Systems – The Digestive System
 Once the bolus is in the stomach, peristalsis
further breaks down the food into chyme.
 Chyme is the combination of digested food with
gastric juices.
 Once in the small intestine the chyme is
completely broken down into nutrients.
 The nutrients are now ready for absorption.
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Organs and Organ Systems – The Digestive System
 Villi and microvilli increase the surface area of the
intestines to allow nutrient absorption.
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Organs and Organ Systems – Regulation of Digestive
Secretions
 Regulation of the digestive
system occurs hormonally.
 Gastrin produce from the
stomach stimulates more
gastric juices to be released.
 Cholecystokinin and secretin
are produced by the small
intestine and they trigger the
pancreas and gallbladder to
release their contents.
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Organs and Organ Systems – Regulation of
Digestive Secretions
 Organ system consists of many organs working
together.
 Failure of one organ may compromise the entire
system.
 Intestine transplants and pancreatic transplants are
becoming more common.
 Gall bladder transplants are rarely done because a
person can live fine without one.
 Organ failure can also disrupt multiple systems.
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Animation: The Digestive System
Click “Go to Animation” / Click “Play”
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Regulating the Internal Environment
 Homeostasis is the ability to maintain a constant
internal environment under changing conditions.
 Thermoregulation is the regulation of temperature to
maintain homeostasis.
 Endotherms maintain body temperature internally and
warmer than the surrounding environment.
 Humans and mammals are examples.
 Ecotherms obtain their body heat from the surrounding
environment.
 Most invertebrates, fish, amphibians and reptiles are
examples.
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BioFlix: Homeostasis
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Regulating the Internal Environment – Negative
Feedback
 Negative feedback occurs when the stimulus that
triggered the change in the body is reversed.
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Regulating the Internal Environment – Positive
Feedback
 Positive feedback occurs when the outcome of a process
increases or intensifies the stimulus for that process.
 During childbirth, hormones cause muscles of uterus to
contract.
 Uterine contractions cause even more hormones to be
released, which intensify the contractions.
 In animals, regulation is usually by negative feedback
because positive feedback often results in amplification –
away from homeostasis.
 Other examples of positive feedback are testosterone
production and urination.
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Regulating the Internal Environment – Organ
Donation
 The best candidates to donate organs are those
who have died of brain injury.
 In cardiac death, organs deteriorate due to lack of
oxygen, and thus are less suitable for transplant.
 Thousands of lives are saved each year through
organ donation.
 The decision to become a donor now can save
families from making difficult decisions later.
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