The Animal Body and
Principles of Regulation
Chapter 43
Organization of Vertebrate Body
• There are four levels of organization:
1.
2.
3.
4.
Cells
Tissues
Organs
Organ systems
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Organization of Vertebrate Body
• Tissues are groups of cells that are similar
in structure and function
• The three fundamental embryonic tissues
are called germ layers
– Endoderm, mesoderm and ectoderm
• In adult vertebrates, there are four primary
tissues
– Epithelial, connective, muscle and nerve
3
Organization of Vertebrate Body
• Organs are combinations of different tissues
that form a structural and functional unit
• Organ systems are groups of organs that
cooperate to perform the major activities of
the body
– The vertebrate body contains 11 principal organ
systems
4
examples
Organization of Vertebrate Body
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Organization of Vertebrate Body
• The body plan of all vertebrates is
essentially a tube within a tube
– Inner tube - Digestive tract
– Outer tube - Main vertebrate body
• Supported by a skeleton
– Outermost layer - Skin and its accessories
• Inside the body are two identifiable cavities
6
Organization of Vertebrate Body
1. Dorsal body cavity - Within skull and
vertebrae
2. Ventral body cavity - Bounded by the rib
cage and vertebral column and divided by
the diaphragm into:
– Thoracic cavity - heart and lungs
•
•
Pericardial cavity: around the heart
Pleural cavity: around the lungs
– Abdominopelvic cavity - most organs
•
Peritoneal cavity - coelomic space around organs
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Organization of Vertebrate Body
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Organization of Vertebrate Body
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Organization of Vertebrate Body
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Organization of Vertebrate Body
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1. Epithelial Tissue
• An epithelial membrane, or epithelium,
covers every surface of the vertebrate body
– Can come from any of the 3 germ layers
– Some epithelia change into glands
• Cells of epithelia are tightly bound together
– Provide a protective barrier
• Epithelia possess remarkable regenerative
powers replacing cells throughout life
12
1. Epithelial Tissue
• Epithelial tissues attach to underlying
connective tissues by a fibrous membrane
– Basal surface - Secured side
– Apical surface - Free side
• Therefore, epithelia have inherent polarity,
which is important for their function
13
1. Epithelial Tissue
• Two general classes
– Simple - one layer thick
– Stratified - several layers thick
• Subdivided by shape into:
– Squamous cells - flat
– Cuboidal cells - cube-shaped
– Columnar cells - cylinder-shaped
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Simple Epithelium
• Simple squamous epithelium
– Lines lungs and blood capillaries
• Simple cuboidal epithelium
– Lines kidney tubules and several glands
• Simple columnar epithelium
– Lines airways of respiratory tract and most of
the gastrointestinal tract
– Contains goblet cells that secrete mucus
15
Simple Epithelium
• Glands of vertebrates form from invaginated
epithelia
• Exocrine glands
– connected to epithelium by a duct
– e.g. sweat, sebaceous and salivary glands
• Endocrine glands
– ductless
– secretions (=hormones) enter blood
16
Stratified Epithelium
• Named according to the features of their
apical (free side) cell layers
– Epidermis is a stratified squamous epithelium
• Characterized as a keratinized epithelium
• Contains water-resistant keratin
• Note: Lips are covered with nonkeratinized, stratified
squamous epithelium
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2. Connective Tissues
• Derive from embryonic mesoderm
• Divided into two major classes
– Connective tissue proper
– Loose or dense
– Special connective tissue
• Cartilage, bone and blood
• All have abundant extracellular material
called the matrix
– Protein fibers plus ground substance
• Ground substance is fluid material containing an
array of proteins and polysaccharides
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Connective Tissue Proper
• Fibroblasts produce and secrete
extracellular matrix
• Loose connective tissue
– Cells scattered within a matrix that contains
large amounts of ground substance
– Strengthened by protein fibers such as:
• Collagen – Supports tissue
• Elastin – Makes tissue elastic
19
Connective Tissue Proper
• Adipose cells (fat cells) also occur in loose
connective tissue
– Develop in large groups in certain areas,
forming adipose tissue
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Connective Tissue Proper
• Dense connective tissue
– Contains less ground substance and more
collagen than loose connective tissue
• Dense regular connective tissue
– Collagen fibers line up in parallel
– Makes up tendons and ligaments
• Dense irregular connective tissue:
– Collagen fibers have different orientations
– Covers kidney, muscles, nerves & bone
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Special Connective Tissue
• Cartilage
– Ground substance made from characteristic
glycoprotein, called chondroitin, and collagen
fibers in long, parallel arrays
– Flexible with great tensile strength
– Found in joint surfaces and other locations
– Chondrocytes (cartilage cells) live within
lacunae (spaces) in the ground substance
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Special Connective Tissue
• Bone
– Osteocytes (bone cells) remain alive in a
matrix hardened with calcium phosphate
• Blood
– Extracellular material is the fluid plasma
– Erythrocytes - red blood cells
– Leukocytes - white blood cells
– Thrombocytes - platelets
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3. Muscle Tissue
• Muscles are the motors of vertebrate bodies
– Three kinds: smooth, skeletal and cardiac
– Skeletal and cardiac muscles are also known as
striated muscles
– Skeletal muscle is under voluntary control,
whereas contraction of smooth and cardiac is
involuntary
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3. Muscle Tissue
• Smooth muscles are found in walls of
blood vessels and visceral organs
– Cells are mono-nucleated
• Skeletal muscles are usually attached to
bone by tendons, so muscle contraction
causes bones to move
– Muscle fibers (cells) are multi-nucleated
• Contract by means of myofibrils, that contain
ordered actin and myosin filaments
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3. Muscle Tissue
• Cardiac muscle is composed of smaller,
interconnected cells
– Each cell has a single nucleus
– Interconnections appear as dark lines called
intercalated disks
– Enable cardiac muscle cells to form a single
functioning unit
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4. Nerve Tissue
• Cells include neurons and their supporting
cells called neuroglia
• Most neurons consist of three parts
– Cell body: contains the nucleus
– Dendrites: highly branched extensions
• conduct electrical impulses toward the cell body
– Axon: single cytoplasmic extension
• Conducts impulses away from cell body
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4. Nerve Tissue
• Neuroglia do not conduct electrical impulses
– Support and insulate neurons and eliminate
foreign materials in and around neurons
• Associate with axon to form an insulating
cover called the myelin sheath
– Gaps, known as nodes of Ranvier, are involved
in acceleration of impulses
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4. Nerve Tissue
• Nervous system is divided into:
– Central nervous system (CNS)
• Brain and spinal cord
• Integration and interpretation of input
– Peripheral nervous system (PNS)
• Nerves and ganglia (collections of cell bodies)
• Communication of signal to body
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Overview of Organ Systems
• Communication and integration
– Three organ systems detect external stimuli and
coordinate the body’s responses
– Nervous, sensory and endocrine systems
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Overview of Organ Systems
• Support and movement
– The musculoskeletal system consists of the
interrelated skeletal and muscular organ
systems
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Overview of Organ Systems
• Regulation and maintenance
– Four organ systems regulate and maintain the
body’s chemistry
• Digestive, circulatory, respiratory and urinary
systems
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Overview of Organ Systems
• Defense
– The body defends itself with two organ systems:
integumentary and immune
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Overview of Organ Systems
• Reproduction and development
– The biological continuity of vertebrates is the
province of the reproductive system
– In females, the system also nurtures the
developing embryo and fetus
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Homeostasis
• As animals have evolved, specialization of
body structures has increased
• For cells to function efficiently and interact
properly, internal body conditions must be
relatively constant
• The dynamic constancy of the internal
environment is called homeostasis
• It is essential for life
35
Homeostasis
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Homeostasis
• To maintain internal constancy, the vertebrate
body uses negative feedback mechanisms
– Changing conditions are detected by sensors
(cells or membrane receptors)
– Information is fed to an integrating center, also
called comparator (brain, spinal cord or
endocrine gland)
– Compares conditions to a set point
37
Homeostasis
• If a deviation is detected, a message is sent
to an effector (muscle or gland)
– Increase or decrease in activity brings
internal conditions back to set point
– Negative feedback to the sensor
terminates the response
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Homeostasis
39
Homeostasis
• Humans have set points for body temperature,
blood glucose concentrations, electrolyte (ion)
concentration, tendon tension, etc.
• We are endothermic: can maintain a
relatively constant body temperature (37oC or
98.6oF)
– Changes in body temperature are detected by the
hypothalamus in the brain
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Homeostasis
• Negative feedback mechanisms often oppose
each other to produce finer degree of control
– Many internal factors are controlled by
antagonistic effectors
• Have “push-pull” action
• Increasing activity of one effector is accompanied by
decrease in the other
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Homeostasis
• Antagonistic effectors are involved in the
control of body temperature
– If hypothalamus detects high temperature
• Promotes heat dissipation via sweating, and dilation
of blood vessels in skin
– If hypothalamus detects low temperature
• Promotes heat conservation via shivering and
constriction of blood vessels in skin
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Homeostasis
room
body
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Homeostasis
• In a few cases, the body uses positive
feedback mechanisms to enhance a change
– These do not in themselves maintain
homeostasis
– However, they are generally part of some
larger mechanism that does!
– Examples:
• Blood clotting
• Contraction of uterus during childbirth
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Homeostasis
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