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Animal Body Systems
Skin Protects the Body
• Integument comes from the Latin word
integumentum , meaning "cover" or "enclosure."
• In animals an integument is any natural outer
covering, such as skin, shell, or membrane.
• The skin makes
up 12-15% of
body weight and
has a surface
area of 1-2
Skin Protects the Body
The human integumentary
system is an external body
covering, but also much
more. It protects, nourishes,
insulates, and cushions. It is
absolutely essential to life.
Without it, an individual
would be attacked
immediately by bacteria and
die from heat or freezing and
water loss.
• The integumentary system is composed primarily of the
skin and accessory structures including hair, nails, and
certain exocrine glands (glands that have ducts or tubes
that carry their secretions to the surface of the skin or
into body cavities for elimination).
Skin Layers
• A flexible and responsive organ
• An organ is any part of the
body formed of two or more
tissues that performs a
specialized function. As an
organ, the skin is the largest
and heaviest in the body
• Composed of 2 principal layers
– Epidermis – outer most layer
– Dermis – inner thicker layer
• Beneath the dermis lies the subcutaneous layer or hypodermis,
composed of adipose or fatty tissue. Although not technically
part of the skin, it does anchor the skin to the underlying
muscles and contains the major blood vessels that supply the
dermis and houses many white blood cells, which destroy
foreign invaders that have entered the body through breaks in
the skin.
Functions of the Skin
• Just think about the differences in the skin of a
fish, a lizard, a frog, a bird, and a mammal.
• Scales, slime, feathers, and hair are all parts of
the integumentary systems for animals.
• The skin protects the underlying organs. The fur
helps insulate against heat loss. Dogs and cats
do not sweat through their skin. They only
sweat from their footpads and nose. They lose
water by panting rather than sweating.
• Outer most layer made
up of an interior and an
exterior part
• Exterior consists of 25 –
30 layers of dead,
flattened cells that are
continually shed
• These dead cells contain
keratin, a protein fiber
that protect the
underneath layers from
exposure to bacteria,
heat and chemicals.
• The epidermis consists of stratified
squamous epithelial tissue.
• Epithelial tissue covers the internal
and external surfaces of the body
and also forms glandular organs.
• Squamous cells are thin and flat
like fish scales.
• Stratified simply means having two
or more layers.
•In short, the epidermis is composed of many layers
of thin, flattened cells that fit closely together and
are able to withstand a good deal of abuse or
friction. It is also waterproof because keratin, a
protein is produced.
• The epidermis can be
divided into four or five
layers. Most important
of these are the inner
and outer layers.
• The inner or deepest cell layer is the only layer
of the epidermis that receives nutrients (from
the underlying dermis). The cells of this layer,
called basal cells, are constantly dividing and
creating new cells daily, which push the older
cells toward the surface. Basal cells produce
keratin, an extremely durable and waterresistant fibrous protein.
• Another type of cell found in
the lower epidermis is the
• Melanocytes produce
melanin, a protein pigment
that ranges in color from
yellow to brown to black.
• The amount of melanin
produced determines skin
color, which is a hereditary
• The melanocytes of darkskinned individuals
continuously produce large
amounts of melanin. Those
of light-skinned individuals
produce less. Freckles are
the result of melanin
clumping in one spot.
• The outermost layer of the
epidermis consists of about
twenty to thirty rows of
tightly joined flat dead cells.
All that is left in these cells is their keratin, which
makes this outer layer waterproof.
• It takes roughly fourteen days for cells to move from
the inner layer of the epidermis to the outer layer.
Once part of the outer layer, the dead cells remain for
another fourteen days or so before flaking off slowly
and steadily. Therefore every 28 days all of the cells of
the epidermis are replaced by new cells.
• The dermis, the second
layer of skin, lies between
the epidermis and the
subcutaneous layer.
Thicker than the epidermis,
the dermis contains the
accessory skin structures.
Hair, sweat glands, and
sebaceous (oil) glands are all rooted in the dermis. This
layer also contains blood vessels and nerve fibers.
Nourished by the blood and oxygen provided by these
blood vessels, the cells of the dermis are alive.
• Connective tissue forms the dermis. Bundles of elastic and
collagen (tough fibrous protein) fibers blend into the
connective tissue. These fibers provide the dermis
strength and flexibility.
• Thickness of the
epidermis varies
in different parts
of the body
depending upon
the function
• Thickest on your
palms and soles
of your feet
Hair Follicles
• Hair grows out of
narrow cavities of the
dermis called hair
follicles that are
supplied with blood
vessels and nerves
and are attached to
muscle tissue
• Many hair follicles
have an oil gland
associated with them
and if the gland is
blocked by oil and
dead cells a pimple
• The upper layer of the
dermis has fingerlike
projections that extend
into the epidermis. Called
dermal papillae, they
contain blood capillaries
that provide nutrients for the basal cells in the
epidermis. On the skin surface of the hands and
feet, especially on the tips of the fingers,
thumbs, and toes, the dermal papillae form
looped and whorled ridges. These print patterns,
known as fingerprints or toeprints, increase the
gripping ability of the hands and feet.
Genetically determined, the patterns are unique
to every individual.
• Within the dermis are sensory
receptors for the senses of touch,
pressure, heat, cold, and pain. A
specific type of receptor exists for
each sensation. For pain, the
receptors are free nerve endings.
For the other sensations, the
receptors are encapsulated nerve
endings. The number and type of
sensory receptors present in a
particular area of skin determines
how sensitive that area is to a
particular sensation. For example,
fingertips have many touch
receptors and are quite sensitive.
The skin of the upper arm is less
sensitive because it has very few
touch receptors.
Functions of the Integumentary System
• Helps maintain homeostasis by regulating
internal body temperature
– Temperature rises, capillaries dilate and blood
flow increases allowing more heat to be lost by
– Cold makes capillaries constrict and heat is
• Sweat is produced as a response to
increased body temperature – heat lost in
evaporation & body cools
• Sense organ – nerve cells receive & relay
• Vitamin production – UV light exposure
produces Vitamin D
• Protective layer shields chemicals and
physical damage
• Cuts allow bacteria to enter - skin repairs itself
Skin Diseases and Problems
Cowpox Lesion
Dermoid cyst, dog
Malignant melanoma, hamster
Pityriasis rosea lesion on pig’s hind
limb. Note the small ring-like early
stage lesions & the older expanding
larger rings healing centrally as
they expand.
Squamous cell carcinomas
Vocabulary Words
Subcutaneous layer
• Stratified squamous
epithelial tissue
Sebaceous glands
Hair follicles
Basal cells
Musculoskeletal System
• The musculoskeletal system
consists of the bones, cartilage,
muscles, ligaments, and
• All vertebrates have a
Musculoskeletal System
• Primary functions of the
musculoskeletal system include
support, motion, protection of
vital organs, and production of
blood cells.
• The skeletal system serves as
the main storage system for
calcium and phosphorus and
contains critical components of
the hematopoietic system.
• Human skeleton has 206 bones (22
bones in human skull)
• Skeleton has two main parts
– Axial skeleton includes the skull and bones
that support it (skull, hyoid bone, vertebral
column, ribs, sternum, etc)
– Appendicular skeleton (hangs) includes
bones of the extremities and structures
associated with them such as the shoulder
and hip bones, pelvic girdle, wrists, ankles,
fingers and toes
• Bone is a connective tissue and one of
the hardest tissues in the body
• Common name of bones differ from
medical names
Bone Structure
•Most bones made of 6 kinds of tissue
•Spongy bone
•Compact bone (solid bone)
Bone Structure
Compact and Spongy Bone
• Bones are composed of two
types of tissue
– Compact – strong, hard outer
layer surrounding every bone
• Stores calcium
– Spongy – contains many
holes and spaces
• Found towards the end of
• Strong and gives bone strength
• Stores calcium too
• Birds have more bone than
other vertebrates (lightens
Haversian Canal
• Haversian canal or osteon are tubular
structures that run the length of the bone
– Osteocytes are live bone cells that receive oxygen
and nutrients from small blood vessels
• Form of connective tissue
that is more elastic and
softer than bone
• Articular cartilage covers
the joint surfaces of bone
• Meniscus is a curved
fibrous cartilage found in
some joints that serves as a
cushion to forces applied to
the joint
Ligaments and Tendons
• Ligaments are bands of tough, fibrous connective
tissue connecting two bones
– Usually found at bone joints where bones connect
• Tendons are thick bands of fibrous connective tissue
that connects muscles to bones
• Produce blood cells in the
bone marrow (the soft
center of the bone)
– Red marrow – hematopoietic
(blood forming) - found in the
humerus, femur, sternum,
ribs, vertebrae & pelvis produces red blood cells,
white blood cells, and cell
fragments for blood clotting
– Yellow marrow – consists of
stored fat cells
Outer Membrane
• Thin sheet of tissue that
covers bone = Periosteum
• Growth area for bone
• Many nerves and blood
vessels supply the bone
through the membrane
• This is the part that hurts
when the bone is bumped
or bruised
• Joint = articulation (join together allowing
• A joint is found where 2 or more bones meet
• Facilitate movement
• Joints held in place by
ligaments – tough bands of
connective tissue
• Movable joints bone ends
covered in cartilage – makes
movement smooth
• Bursae are fluid filled sacs that
act like a cushion in areas with
friction. They are found on the
outside of the joint decreasing
friction and keeping bones and
tendons from rubbing against
each other
Joints are classified based on the
degree of movement they allow
– The ball-and-socket joint is
found in hip-bones and shoulders;
allows the most movement of all
the joints. One bone (like the
femur) has a ball-like knob at the
end of it, & the knob fits into a
cup-like space on the other side.
The ball-and-socket joint is what
allows baseball pitchers to throw
a ball with tremendous speed.
– The sliding joint is found in the
vertebral column and allows small
sliding movements. The vertebrae
have pads of cartilage between
them, and the bones slide over
these pads. This is what makes
the backbone so flexible.
Joint Types
Joint Types
– The pivot joint allows
movement turning from side to
side, and your head is attached
to your vertebral column with
this joint. A hole in one bone fits
over a pointed part of the other
bone, so that one bone can turn
on top of the other.
– The hinge joint allows bones to
move back and forth, and is
found in your elbow and knee. It
allows bones to move like a
hinge in a door.
1. fixed joint 2. pivot joint 3. ball-and-socket joint
4. sliding joint 5. hinge joint
Formation of Bone
• Ossification is the formation of bone from
fibrous tissue
• Vertebrate skeletons are made of cartilage
when they are born
Formation of Bone
• Humans begin to replace
the cartilage with bone by
the 9th week
• Blood vessels penetrate
the membrane covering
the cartilage and
stimulate its cells to
become bone cells called
Formation of Bone
• Osteoblasts are immature
bone cells that produce bony
• Osteoblasts secrete collagen
to which minerals (calcium
salts, etc) are deposited
turning the osteoblasts into
• Adult skeleton almost all bone
except for where flexibility is
needed (nose tip, external
ears, discs between vertebrae
and movable joint linings)
Bone Growth
• Bone tissue is alive and made of cells
• Growth occurs in length and diameter
– Length at ends of bones in cartilage plates
– Diameter at outer surface
• Increased production of sex hormones during teen years
causes rapid osteoblasts cell division resulting in a growth spurt
• After growth stops, bone-forming cells responsible for repair
and maintenance of bone
• Bone Growth Movie
Functions of the Skeletal System
• Provides a framework for body tissues
• Protection of internal organs(heart, lungs, brain)
• Skeleton provides attachment points for
Bones Store Minerals
• Store calcium and phosphate among other
• Calcium responsible for bone strength
– Sources milk, yogurt, cheese, lettuce, spinach and
dark leafy vegetables
Bone Minerals
Injury & Diseases of Bones
• Forcible twisting of a joint is a sprain
and the injury occurs at the bursae,
ligaments, or tendons
• Arthritis is an inflammation of the
joints caused by infections, aging or
– Bone spurs are outgrowths of bone
(form of arthritis)
• Osteoporosis – loss of bone volume
and mineral content causing bones
to become more porous and brittle
• Broken bones – bones are realigned
and immobilized until bone tissue
Diseases and Injuries of the
Musculoskeletal System
• Because many body systems,
including the nervous, vascular,
and integumentary systems, are
interrelated, disorders of one of
these systems may also affect the
musculoskeletal system and
complicate diagnosis.
• Diseases of the musculoskeletal
system most often involve motion
deficits or functional disorders. The
degree of impairment depends on
the specific problem and its
severity. Skeletal and articular
disorders are by far the most
• Tendons act as bridging and attachment
structures for the muscles
– Some bridge long gaps between the muscles
and target bone and, therefore, are prone to
injury themselves.
– An example is the superficial flexor tendon of
horses, which is frequently injured by partial
tearing that leads to tendinitis.
• Another acquired tendon injury involves
traumatic disruptions. Due to the
relatively poor blood supply of both
tendons and ligaments, healing is
delayed and frequently poor.
• Management of injuries to
ligaments and tendons requires
patience and long-term
• Bone diseases are generally
congenital or hereditary,
nutritional, or traumatic.
– Congenital disorders include in
utero malformations and
atavisms, such as polydactyly or
persistent ulnae or fibulae in
– Genetic defect examples are
atlanto-occipital malformations
in Arabian horses or certain
cases of spinal ataxia, canine
hip dysplasia, and abnormal
bone formation such as that
caused by parathyroid
Bilateral hip dysplasia
in a dog
Normal hips in a dog
• Nutritional diseases are caused primarily
by imbalances or deficiencies in minerals
– particularly copper, zinc, and magnesium.
– Calcium and phosphorus concentrations
must also be present in the correct ratio.
• Osteomalacia is an example of
imbalanced or deficient calcium and
phosphorus intake.
– Other nutritional disorders are caused by
excessive protein intake of growing animals.
• Either deficiency or excess intake of
some vitamins (vitamins A and D) may
influence growth and development of
bone (Rickets)
• Aseptic physitis or special
osteochondrotic conditions may be
caused by zinc toxicity or copper
ossification of the cartilage
Of Rickets
• Traumatic causes of bone disorders
represent the vast majority of cases
and including fractures, fissures.
• Lack of weight bearing, reduced
motion, instability, pain, heat, or
swelling usually accompany these
• Diagnostic procedures include
inspection, manual palpation,
diagnostic imaging (such as
radiography, ultrasonography, or
thermography, and increasingly
scintigraphy, computed tomography,
or MRI), and diagnostic anesthesia
to determine the specific anatomic
structure or region involved in the
PET Scan (top) and
Thermography of a cat
are branches of Nuclear
Medicine that uses
radioactive isotopes
• Chronic inflammation of
joints and surrounding
structures is most
common in articulations
associated with
locomotion, although
other joints may
occasionally be
• Normal synovial fluid
lubricates the synovial
tissues in a joint by
lubrication and the
articular cartilage.
Vocabulary Words
Axial Skeleton
Appendicular skeleton
Compact bone
Red marrow
Yellow marrow
• Osteocyte
• Spongy bone
• Compact bone
• Half of your body mass is
• Humans have more than 600
• Muscular system is all the
muscles in your body
• Muscles are groups of fibers
or cells that are fused together
in a bundle
• They can change their shape
and length to cause
Muscle Types
• Three types of muscle fibers
– Smooth muscle
– Cardiac muscle
– Skeletal muscle
• Each has a different structure and pattern that
make it different from the others
Smooth Muscle
• Found in walls of your internal
organs and blood vessels,
digestive and reproductive tracts
• Made of sheets of cells that are
elongated and spindly
• Not connected to bone
• Most common function –
involuntary muscle movement squeeze so that pressure is
exerted on the inside of the tube
or organ it surrounds to move
material through it (peristalsis,
movement of gametes)
• Spindle shaped with one nucleus
per cell
Cardiac Muscle
• Involuntary muscle (you can’t
control – your brain controls)
that makes up your heart
• Tightly interconnected and
form a network that allows
the heart to contract
• Not connected to bone
• Conducts electrical impulses
necessary for rhythmic
• Bundles of fibers striated
(striped from 2 kinds of
proteins that make it up)
Skeletal Muscle
• Attached to bones for
• Majority of muscle in
body is skeletal muscle
• Voluntary muscle –
movement is under your
• Striated – two kinds of
proteins make it up
• Most meats that you eat
are skeletal muscle
Skeletal Muscle Contraction
• Most work in opposing pairs
– Muscles can only shorten
– Takes a pair of muscles to
move bones back and forth
• One muscle contracts the other
in the pair relaxes
• Muscles made of muscle
fibers that are long fused
muscle cells
• Involuntary muscles must
be stimulated by a nerve
• Muscles only move when a
muscle is contracted
– Contraction shortens the
Fast and Slow Twitch
• Fast Twitch (Type II) uses
anaerobic metabolism to create
fuel; good for short bursts of
strength; fire more rapidly; Two
types (Olympic Sprinters have
80% fast twitch fibers)
– Type IIa – intermediate fast twitch
use aerobic and anaerobic
metabolism and are a combination of
Fast and Slow Twitch muscle fibers
– Type IIb – Uses anaerobic
metabolism to produce powerful,
quick bursts of speed but fatigues
• Slow Twitch (Type I) – fire more
slowly; muscles more efficient at
using O2 to generate more ATP
for constant muscle contractions;
can go a long time before they
fatigue (marathon runners)
• Myofibrils are smaller
units of muscle fiber
that is composed of
thick myosin protein
filaments and thin actin
protein filaments
• Myofibrils can be
divided into sections
called sarcomeres
(functional unit of
Muscle Contractions
• Connected to bone by tendons
• Tendons cause the bone to be
pulled when the muscle
• When you flex your muscles you
are contracting them & they
bulge through the skin
Sliding Filament Theory
• Explanation of
how muscle
contraction occurs
• “When signaled,
the actin filaments
within each
sarcomere slide
toward one
shortening the
sarcomeres in a
fiber and causing
the muscle to
• Myosin filaments
do not move
Muscle Strength and Exercise
• The number of muscle fibers in
a muscle are fixed when you
are born
• Strength depends upon the
thickness of the fibers & on how
many contract at one time
• Regular exercise stresses
muscle fibers slightly and to
compensate for this added
workload, the fibers increase in
diameter by adding myofibrils
• Regular exercise improves
muscle performance
Lactic Acid
• Muscle cells continuously
supplied with ATP from
aerobic and anaerobic
• Anaerobic processes form
lactic acid that builds up in
muscle cells.
• Acid moves into the blood
increasing respiration rate &
blood becomes more acidic
• Lactic acid broken down
when excess oxygen is
Fatigued Muscles
Cardiac Muscle
Skeletal Muscle
Smooth Muscle
Involuntary Muscle
Voluntary Muscle
Sliding Filament Theory
Cardiovascular System
• AKA Circulatory System
• Pertains to the heart and
blood vessels
– Includes the heart, blood
vessels and blood
• Essential to support life of
each of the millions of cells
that makes up an animal
• Blood has a wide range of
functions to maintain the
animal’s health
• Heart and blood provide an
access path to all the body
Blood Components
• Centrifuged blood separates
into cellular portion
thrombocytes, and
leukocytes) and plasma
(water and protein)
• Cellular portion of the blood
makes up 30 – 45%
depending upon animal age
and species
Blood Proteins
• Three types
– Albumin – major blood
protein – water maintenance
• Draws water into blood stream
by osmosis
• Produced in the liver
– Globulins
• Antibodies produced by
immune system
– Fibrinogen
• Aids in clotting blood
Cellular Component
• Three types
– Erythrocytes or Red blood cells
– Leukocytes or White blood cells
– Thromboctyes or Platelets
Carry oxygen
Biconcave disk
Produced in bone marrow = erythropoiesis
Lifespan varies: Dog 100-110 days; Cat 66-78
• Erythrocytes low in blood - kidney releases
erythropoietin stimulating bone marrow to
produce more RBC
• Contain Hemoglobin – iron containing molecule
that gives blood the red color
• Efficient at binding oxygen
– carrying 97% of the oxygen
• Highest oxygen content in the lungs and it gets
lower as it is pumped through tissues & organs
• Higher CO2 concentrations in tissues & lower pH
(lactic acid) increases amount of O2 released
• Carries 20% of CO2 that is converted to
bicarbonate and transported to the lungs
• Absorbs many free H+ ions lowering pH
• Help fight infection
• 5 major types each with different functions:
Neutrophils, lymphocytes, eosinophils, monocytes,
and basophils
• Produced in bone marrow
• Found in the blood or in tissues to fight infection
• A normal dog has 6000-7000 WBCs/microliter
• Phagocytize and
microorganisms in
tissues and usually not
in the blood
• Nucleus appears
segmented or divided
• Phagocytize microbes
• Produced in the marrow then move to the blood
and into tissues
• Mature into macrophages that establish in the
liver or lungs
• Remove microorganisms,
dead cells and foreign
• Look similar to neutrophils
with segmented nucleus
• Have a large number of
visible granules in the
• Roles in fighting parasites
and in allergic reactions
• Granules help to control
• Many granules with a segmented nucleus
• Involved in allergic reactions
• Some granules contain histamine
– Histamine causes inflammation in the linings of the
nasal passages and respiratory tract producing
sneezing and runny noses
Have a single nucleus
Produce antibodies to help fight disease
Make up a portion of globulin found in plasma
Found in all organs and tissues involved in
fighting infection (tonsils, lymph nodes, spleen,
• Neutrophils and lymphocytes make up the
largest number of WBCs in the circulation blood
Produced in bone marrow
Aid in normal clotting of the blood
Only damaged vessel stimulates a clot
Very complicated process involving platelets
and numerous proteins and factors in the blood
– Blood vessel is cutvessel constrictsplatelets
begin to attach to the edges of the damaged
vesselclotting factors convert fibrinogen to fibrin
completing the plugover time fibrin is replaced
with repaired blood vessel
Useful in diagnosing disease
Numerous blood tests available
Hypo = value below normal
Hyper = value above normal
Anemia = low red blood cell count
– Less oxygen supplied to tissues
– Fatigue during exercise usually first symptom
– 3 common causes
• excessive blood loss
• Shortened RBC life span
• Decreased RBC production
– Body attempts to correct anemia by releasing as many
RBC’s as possible – some immature without nucleus
Blood Clotting in Animals
• Quite impressive
• Farm cat with leg amputated by farm machinery
can stop bleeding without intervention
Blood Functions
• 2 major functions
– Transport substances
throughout the body
• Oxygen, carbon dioxide,
nutrients, wastes,
electrolytes and
– Protect the body from
infection and diseases
Mammalian Heart Structures
• Heart is located inside the thoracic cavity
• 4 chambered heart making 2 separate circulatory paths
– Pulmonary side pumps blood to the lungs
• Exchanges oxygen and carbon dioxide
– Systemic circulation delivers blood to the body
• Delivers oxygen rich blood and nutrients to the organs
Structures of the Heart
• Located low in the chest
between two lungs
• Surrounded by the pericardium thin membrane
– Pericardium filled with pericardial
fluid to prevent friction between the
heart and the pericardium when the
heart beats
• Hollow organ divided into 4
• Valves keep blood flowing in one
– Present in all major vessels leaving
the heart
• Muscular septum separates right
and left sides
Heart Walls
• Heart is made of 3 walls
– Epicardium = external
layer of the heart
– Myocardium = middle
and thickest layer of the
heart this is the actual
heart muscle
– Endocardium = inner
layer of the heart – lines
the heart chambers and
Coronary Arteries
• Called coronary arteries because
they look like a crown
• Supply blood and nutrients to the
• Coronary veins remove wastes
from the myocardium
• Disruption of blood flow may be
coronary occlusion (blocked)
– Ischemia is a deficiency of blood
supply to an area
– Ischemia can lead to necrosis (death
of tissue) the area is called an infarct
Blood Vessels and Blood Flow
• Opening within a vessel is the lumen
– Diameter affected by constriction
or dilation
– Vasoconstrictors and vasodilators
contract or dilate the vessels
• Blood returns to the heart from the
systemic circulation via large
vessels called vena cava
– In front of heart blood returns by
cranial vena cava
– Behind heart through caudal
vena cava
– Human anatomy
• Superior vena cava = cranial
vena cava
• Inferior vena cava = caudal
vena cava
Blood Circulation
• Vena cavaright
atriumright ventricle (via
right atrioventricular
valve)lungs (via
pulmonary artery through
pulmonary semilunar
valve)left atrium (via
pulmonary vein)left
ventricle (via left
atrioentricular valve)aorta
(via aortic semilunar
ulesveinsVena cava
Heart Facts
• Blood returning through the
vena cava is low in oxygen,
high in wastes and CO2
• Valves in the heart and in
major arteries leaving the
heart keep blood from
flowing backwards
• The left ventricle is the
thickest wall of the heart
• Veins have thinner walls than arteries
• A muscular septum divides the left and right side of the heart
• Major branches off aorta: carotid (head and brain), mesenteric
(gastrointestinal tract), renal (kidneys), iliac (hind legs)
Heart Rate
• Rate of heartbeat is
partially controlled by
the nervous system
through electrical
stimulation of the
• Beat begins within the
heart by pace maker
cells without input
from the nervous
Pacemaker System
Pacemaker system keeps heartbeat and contractions
regular and organized
– Atrial contraction followed by
ventricular contraction
– Mammals pacemaker called
sinoatrial (SA) node that is
found in the wall of the right
atrium near the entrance of
the superior vena cava
– Purkinje fibers - specialized
cells in right atrium signal SA
node to spread electrical
signal to surrounding muscle
– Atria contract; blood pushed into the two ventricles
– Signal picked up by the atrioventricular (AV) node
– Conducting fibers carry electrical stimulus to the ventricles
and ventricles contract
Cardiac Cycle
• A cardiac cycle is one complete contraction and
relaxation period
• Rate varies by species
• Pulse the rhythmic expansion and contraction of an
artery produced by pressure created as blood surges
through veins
• Atria fills with blood
during relaxation or
diastole phase
• Systole phase is during
the contraction
2 complete cycles
Blood Pressure
• Tension exerted by blood on
the arterial walls
• Blood pressure is taken during
both phases of cardiac cycle
and is measured by a
– Hypertension = high blood
pressure/hypotension = low
– Higher (first) number is during
systole phase the second (lower)
number is diastole phase
Blood Pressure
– Measured in mm Hg
– Human typical blood pressure is 120/80
– Blood pressure varies for each species and for
fitness levels
– Blood pressure increases heart rate decreases
(impulse from vagus nerve)
– Blood pressure decreases heart rate increases
(impulse from vagus nerve)
– Pressure much higher in arteries than in veins
• Flow of ions that incites cardiac muscle contraction causes a
small electrical current
• Electrocardiograph is an instrument that measures these
electrical currents
• Electrocardiogram (ECG) is a tracing made of the currents
• ECG identifies problems associated with the contraction of the
– Changes in the size of the heart or damaged portions can be detected by
changes in the sizes or shapes of the peaks on the ECG
Heart Rhythms
• Sinus rhythm = normal consistent rate &
• Arrhythmia =change in rate,
rhythm/conduction in the heart
• Sinus tachycardia is a faster than normal rate
• Sinus bradycardia is a slower than normal
• Sinus arrhythmia = heart rate increases
w/inhale and decreases w/exhale
• Atrial fibrillation =SA node not acting as
pacemaker – atria quivers instead of
contracting correctly
• Ventricular fibrillation = Site in ventricle fires
very rapidly making the ventricle quiver
instead of contracting. Most serious
arrhythmia; requires defibrillation
• Asystole = Heart no longer contracting =
cardiac arrest
Heart Rate
• Several factors influence heart rate
– Disease
– Fear
– Nervousness
– Shock
Heart Murmurs
• Sound made by a defective valve
or abnormal blood flow
• A swishing noise caused by a leak
in a valve
– Results from the inability of the valve to perform or close
• AV valve leak =systolic murmur (occurs during
contraction of ventricles)= lub-swish-dub
• Aortic valve leak = diastolic murmur (blood leaking
back into ventricle as it relaxes) = lub-dub-swish
Cardiac Output
• Amount of blood pumped in one
• Capable of increasing
dramatically when needed (ex:
horse running a race)
– Heart rate increases
– Amount of blood increases
• Cardiac Output in mL/min = heart rate (beats/min) X stroke volume
• An average person has a resting heart rate of 70 beats/minute and a
resting stroke volume of 70 mL/beat. The cardiac output for this
person at rest is:
• Cardiac Output = 70 (beats/min) X 70 (mL/beat) = 4900 mL/minute.
• The total volume of blood in the circulatory system of an average
person is about 5 liters (5000 mL) and it is pumped through the heart
about once a minute in a healthy adult.
• Inadequate tissue perfusion = not enough blood
pumped to the vital organs
• Animals are weak and depressed
• Heart rate is rapid and weak
• Low capillary refill time (press on gums and
pink color should return in 1 second)
Heart Failure
• Commonly affects elderly pets specially if they
have a heart murmur
• Heart enlarges and beats rapidly
• Cough develops from enlarged heart putting
pressure on the airway
• Fluid accumulates in the lungs or abdomen
• Condition eventually fatal
Pathologic Conditions
Artherosclerosis = hardening and narrowing of the
Congestive heart failure = retention of fluid and edema
(fluid in intercellular spaces) as a result of insufficient
cardiac output
Carditis = inflammation of heart
Pericarditis = inflammation of pericardium
Myocarditis = inflammation of myocardium
Endocarditis = inflammation of endocardium and
sometimes heart valves
Vasculitis = inflammation of blood vessel
Aneurysm = balloon-like enlargement of artery
Hemangioma = benign tumor of newly formed blood
Pathologic Conditions
Thrombus = blood clot attached to artery or vein
Embolus = foreign object circulating in blood
embolism = blockage of blood vessel
Cardiomyopathy = disease of heart muscle
Hypoxia = below normal oxygen levels
Dirofilariasis = heart worm infection
Congenital = present at birth
Anomaly = deviation from normal
Idiopathic = unknown cause
Iatrogenic = produced by treatment
Respiratory System
• Brings O2 into the
body and blood
delivers it to cells
• Respiration =
exchange of gases
between the
atmosphere and
body cells
• Ventilation =
breathing fresh air
Respiratory Tract
• The respiratory
tract is divided into
upper and lower
– Upper = nose,
mouth, pharynx,
epiglottis and
– Lower = trachea,
bronchial tree and
Upper Respiratory Tract
• Air enters and exits the body
through the nose
• Nose consists of nostrils or
nares that are paired and is
divided by cartilage called
the nasal septum
• Endotherms have nasal
turbinates–scroll-like bones
covered with vascular
mucous membranes that
warm, moisturize and filter
inhaled air
Upper Respiratory Tract
• Lined with mucous
• Mucous from
glandular secretions
and cilia help filter the
air to remove debris
• Olfactory receptors,
responsible for smell
are nerve endings in
the mucosal lining
Upper Respiratory Tract
• Sinus is a fluid or air filled
sac in the bone that
produce mucous, make
bone lighter and aid
formation of sounds
• Air passes through the
nasal cavity to the
pharynx carrying air &
food; pharynx = throat
• Pharynx connects nasal
passages to larynx and
mouth to esophagus
Divisions of the Pharynx
• Nasopharynx –
passageway of air
entering through the nose;
located posterior throat to
the nasal cavity & above
the soft palate
• Oropharyns - throat
between the soft palate &
epiglottis; air passageway
• Laryngopharynx – throat
below epiglottis that
opens into the voice box
and esophagus; food
entering mouth’s
Other Upper Respiratory
Tract Structures
• Soft Palate – closes off the
nasopharynx to prevent
food from going up the nose
during swallowing
• Epiglottis acts like a lid
covering the larynx during
swallowing to keep food
from entering trachea and
going into the lungs
• Larynx is a firm cartilage structure between the
pharynx and the trachea & is called the voice box
• Opening to the major airways (you can feel yours at
the top of your neck)
• Contains the vocal folds (cords) – paired membranous
bands in the larynx that help produce sound
• The vocal apparatus
consisting of vocal cords
and the space between
• Air passes through glottis
causing a vibration that
produces sound
• In avian species the
syrinx is the vocal
apparatus and it is
located between the
trachea and bronchi
Respiratory System
• Epithelium covered with
mucus that filters the air by
trapping particles that are
eventually swallowed
– Mucus is moist and it keeps the
lungs from loosing moisture
• Increases the surface area
allowing air to contact a
large amount of epithelium
and the air warms up close
to body temperature before
it enters the lungs
• Larynx leads to the trachea
also called the windpipe
• Passes into the thorax
• Trachea is ventral to the
esophagus and held open by a
series of C-shaped cartilage
– Open part of C is adjacent to
esophagus makes swallowing
easier C’s joined by connective
• Cartilage allow neck to move
without pinching off the air flow
• Lined with smooth epithelium
and mucous coated cilia for
catching tiny particles
• Mucus with particles is worked
back up to the larynx then
Tracheal collapse –
During inspiration,
the trachea in the
neck tends to collapse
• Trachea enters the chest and branches into
two major bronchi that each lead to a lung
• Bronchi divide into smaller and smaller
airways forming the bronchioles
– divisions of Bronchi
resemble tree
branches and is
called the bronchial tree
– Bronchioles have
smooth muscle in
their walls allowing
airway to dilate or
• Bronchioles lead to
smallest openings the
– Contain no cartilage or
– Gas exchange occurs
between alveoli and
– Branch terminate into
– 1. Trachea 2. Mainstem bronchus
3. Lobar bronchus
4. Segmental bronchus
5. Bronchiole 6. Alveolar duct
7. Alveolus
• Alveoli coated in surfactant that keeps them
from collapsing and lowering the amount of
pressure required to inflate
– Thin flexible membrane wall surrounded by capillaries
– Prematurely born animals may lack surfactant (fatal)
• Thoracic cavity is contained within the ribs
• The main organ of respiration is the lungs
• Lungs are divided into lobes (well defined portion)
and the number of lobes differs between species
• Area between the lungs
is the mediastinum and
is where you would find
the heart, aorta, lymph
nodes, esophagus,
trachea, bronchial tubes,
nerves thoracic duct &
• Lungs contain an enormous
collection of alveoli,
bronchioles and bronchi
• Lungs look and feel spongy
with air trapped and elastic connective tissue that
holds airways together
• Lungs covered with smooth epithelial membrane
called pleura (also lines the thorax)
• Fluid between the pleural layers provides lubrication to
prevent friction
• In healthy animals lungs will touch the chest wall
during inhalation
• Muscle separating
thoracic & peritoneal
• Causes air pressure
in lungs to drop
below atmospheric
pressure producing a
vacuum in thoracic
cavity to draw in air
• Diaphragm relaxes
air is forced out
• Innervated by
phrenic nerve
• Inhalation
(Inspiration)– air
taken into lungs –
chest cavity volume
• Exhalation
(expiration) – air
forced out of lungs –
chest cavity volume
• Difficulty in breathing
= dyspnea
• Intercoastal Muscles between the ribs raise the
ribs and expand the chest
• Diaphragm contracts; moves towards the abdomen
• Pressure in the lungs is lowered allowing air to flow
into the lungs
• Intercoastal Muscles relax; ribs lower
• Diaphragm relaxes arching forward toward chest
• Elastic tissue in lungs recoils driving air out
Respiration Rate
• Respiration Rate = breaths per minute
• Brain controls the normal rate of respiration
• Factors influencing respiration rates
Heat (hot day)
Nervousness (trip to the vet)
Activity level
Panting (for cooling) Cools blood in
pharynx blood vessels that lowers the
body temp
as cooler blood circulates
– Oxygen plays a small part in respiration rate –levels must
fall very low before they stimulate respiration but CO2
levels quickly stimulate respiration
Normal Respiration Rates
Respiration Rate
Guinea Pig
Exercise & Respiration
• Muscles produce more
CO2 when animal is active
stimulating faster
• Special receptors in major
arteries detect the increase
of CO2 in the blood and
send signals to the brain
• Bronchioles are stimulated
to dilate opening airways
and improving air delivery
to alveoli
• Breathing is an involuntary process but it can be
controlled consciously (ex: holding your breath)
Pulmonary air-sac system of a Common Teal (Anas crecca) with blue highlighting the location of air
sacs .b, Main components of the avian flow-through system. Abd, abdominal air sac; Cdth, caudal
thoracic air sac; Cl, clavicular air sac; Crth, cranial thoracic air sac; Cv, cervical air sac; Fu, furcula;
Hu, humerus; Lu, lung; Lvd, lateral vertebral diverticula; Pv, pelvis; and Tr, trachea (From: O'Connor and
Claessens 2005)
• A protective reflex action usually caused by the irritation of sensitive
nerve endings in the mucous membrane that lines the nose
• Large amount of air forced through nose and mouth forcing trapped
particles out
• Nasal discharge categorized by character: serous (clear), mucoid
(cloudy), blood tinged, bloody (epistaxis) or a combination of these.
• It is also categorized by location: unilateral (one nostril vs. bilateral
(both nostrils); chronicity (acute vs. chronic); and associated signs of
disease. For example, nasal bleeding could suggest injury, a tumor,
bleeding disorder or a tick-borne infection.
• When foreign particles enter the larynx and trachea
and they initiate the coughing reflex
• Air is first inhaled, then the epiglottis and vocal folds
close and the animal begins to exhale forcefully
opening the epiglottis and vocal folds allowing air to
rush out with great force
• Kennel Cough - The most common cause in dogs is
the bacteria Bordetella bronchiseptica. The bacteria
becomes airborne when an infected dog breathes,
barks and coughs, then the bacteria is inhaled by
another animal, resulting in kennel cough transmission
• Phlegm – thick mucus secreted by respiratory lining
that is ejected through the mouth it is called sputum
(can be used for cytologic examination/testing)
Clinical Practice
• Cyanosis – blood has a darker bluish color when
oxygen levels are too low – indicated inadequate
oxygen being delivered to tissues
• Pneumonia – inflammation in the lungs usually caused
by an infection (viral or bacterial)
– White blood cells try to fight infection; cells and tissue fluid
accumulate in alveoli; decrease in lung capacity and
effectiveness of gas exchange
• Bubbling – sound of popping bubbles suggesting fluid
• Pleural friction rub - pleural noise indicating lungs and
chest are inflamed and irritated
• Crackles and Wheezes – noises that indicate
inflammation, fluid or both in the lungs
Clinical Practice
• Hypoxia – inadequate O2 supply to body tissues
• Hypercapnia – excessive CO2 in blood (Hypocapnia
decrease in CO2 levels in blood)
• Respiratory acidosis – excessive CO2 in blood
lowering blood pH (respiratory alkalosis – abnormally
low CO2 levels raising pH)
• Hyperventilation - abnormal increase in respiration
• Indotracheal intubation – passage of a tube through
the oral cavity, pharynx and larynx into the trachea
• Chest tube – tube inserted into thoracic cavity to
remove gases or fluids
Clinical Practice
• Cats/kittens with runny eyes, nasal discharge,
sore throat, fever, coughing and sneezing not
unusual for all cats in house to develop the
symptoms – since disease causing organisms
are highly contagious
• Horses have much larger lungs than cattle of
the same size
– Roaring – one vocal fold fails to open air has ½
opening to enter/exit
– Heaves – coughing, nasal discharge, labored
breathing and easily tire from exposure to dust and
mold – bronchodialators are given to open airway
and decrease inflammation
A smoker's dissected
heart and lungs show
black spots from tar.
Cross section of a human lung.
The white area in the upper
lobe is cancer; the black
areas are discoloration due
to smoking
Endotracheal tube
Pleural fraction rub
Soft Palate