Organization of Vertebrate Body. Organization of Vertebrate Body

Transcription

1 The Animal Body and Principles of Regulation Chapter 43 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 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 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 5 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 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

2 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 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 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 14 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 15 Simple Epithelium Simple Epithelium (Cont.) Simple Epithelium

3 Simple Epithelium (Cont.) Simple Epithelium Stratified Epithelium 19 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 20 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 21 Stratified Epithelium Connective Tissues Connective Tissue Proper 22 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 23 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 24 Connective Tissue Proper Connective Tissue Proper Connective Tissue Proper 25 Adipose cells (fat cells) also occur in loose connective tissue -Develop in large groups in certain areas, forming adipose tissue 26 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 27 3

4 Connective Tissue Proper Connective Tissue Proper (Cont.) 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 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 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 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

5 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 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 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

6 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 46 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 47 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 48 Reproduction and development -The biological continuity of vertebrates is the province of the reproductive system (Cont.) -In females, the system also nurtures the developing embryo and fetus (Cont.) (Cont.)

7 (Cont.) (Cont.) (Cont.) (Cont.) (Cont.) 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

8 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 -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 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 (37 o C or 98.6 o F) -Changes in body temperature are detected by the hypothalamus in the brain 67 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 68 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 69 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 70 -Contraction of uterus during childbirth