The Animal Body andPrinciples 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

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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

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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

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Organization of Vertebrate Bodyex

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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

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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

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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

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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

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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

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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

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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

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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

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