the animal body and organization of vertebrate body ... · pdf filechapter 43 2 organization...

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The Animal Body and Principles of Regulation

Chapter 43

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Organization of Vertebrate Body

There are four levels of organization: 1. Cells 2. Tissues 3. Organs 4. Organ systems

Bodies of vertebrates are composed of different cell types -Humans have 210

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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

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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

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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

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Dorsal body cavity: Within skull & vertebrae Ventral body cavity: Bounded by the rib

cage and vertebral column -Divided by the diaphragm into: -Thoracic cavity: Heart and lungs -Abdominopelvic cavity: Most organs -Peritoneal cavity: Coelomic space -Pericardial cavity: Around the heart -Pleural cavity: Around the lungs

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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

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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

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Epithelial Tissue

Two general classes -Simple = One layer thick -Stratified = Several layers thick

Subdivided 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: secrete mucus

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Simple Epithelium

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Simple Epithelium (Cont.)

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Simple Epithelium

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Simple Epithelium (Cont.)

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Simple Epithelium

Glands of vertebrates form from invaginated epithelia -Exocrine glands -Connected to epithelium by a duct -Sweat, sebaceous and salivary glands -Endocrine glands -Ductless; lost duct during development -Secretions (hormones) enter blood

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Stratified Epithelium

Named according to the features of their apical 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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Stratified Epithelium

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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

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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

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Adipose cells (fat cells) also occur in loose connective tissue -Develop in large groups in certain areas, forming adipose tissue

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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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Connective Tissue Proper (Cont.)

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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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Bone -Osteocytes (bone cells) remain alive in a matrix hardened with calcium phosphate -Communicate through canaliculi

Blood -Extracellular material is the fluid plasma -Erythrocytes = red blood cells -Leukocytes = white blood cells -Thrombocytes = platelets

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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 the other two is involuntary

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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, which

contain ordered actin & myosin filaments

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Muscle Tissue

Cardiac muscle is composed of smaller, interconnected cells -Each with 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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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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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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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

Support and movement -The musculoskeletal system consists of two interrelated organ systems

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Regulation and maintenance -Four organ systems regulate and maintain the body’s chemistry -Digestive, circulatory, respiratory

and urinary systems

Defense -The body defends itself with two organ systems: integumentary and immune

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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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Overview of Organ Systems (Cont.)

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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

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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

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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

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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

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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 72

Homeostasis

the animal body and organization of vertebrate body ... · pdf filechapter 43 2 organization...

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