Tissue Types
• Cells are the building blocks of tissues
• The human body has four tissue types
– Epithelial
–
Connective
– Muscular
–
Nervous
Epithelial Tissue
• Epithelial tissue covers the body, lines all cavities, and composes the glands
– Capable of secretion, absorption, protection, filtration
– Has few blood vessels and not many extracellular substances between the cell
– Identified by the number of cell layers and the shape of the cells in the outermost layer
•
• There are eight basic types of epithelium
– Six identified by both the number of cells and their shape
Epithelial cells can be flattened, cube-like, or columnar
–
Each shape mirrors the function of the tissue
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Epithelial Tissue
Connective Tissue
•
•
• Connective tissue connects the structures of the body
– Binds, supports, and anchors the body
–
Is the most abundant type of tissue in the body
– Often has rich blood supply and nervous tissue
Connective tissue is composed of cells suspended in a noncellular matrix
The matrix is secreted by the fibroblasts and other cells
– May be liquid, gel-like, or solid
– The matrix determines the characteristics of the connective tissue
– Contains collagen (for strength) and elastin (for flexibility, stretch, and recoil)
– Or contains inorganic calcium phosphate that is very hard
• Two classifications
– Soft connective tissue and specialized connective tissue
Soft Connective Tissue
•
Soft connective tissue has a semi-fluid matrix
– Has fibroblast cells that secrete fibers
– Also has white blood cells that fight infection
– The matrix can be loosely or densely packed
• Soft connective tissue includes
– Loose connective tissue (examples - fills in spaces between organs)
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• Also called areolar connective tissue
Dense connective tissue (examples - tendons, ligaments)
• Regular or irregular
–
Elastic connective tissue
• Used to create structures that can stretch (examples – found in various locations such as in lungs and some blood vessels)
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Soft “Loose” Connective Tissue
Soft “Dense Regular” Connective Tissue
Soft “Elastic” Connective Tissue
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• Cartilage
• Bone
• Blood
• Lymph
• Adipose
Specialized Connective Tissue
Specialized Connective Tissue – “Cartilage”
• Cartilage is a unique connective tissue because it is avascular
– Other types of connective tissue all have rich blood supplies
• Cartilage heals slowly because nutrients must diffuse through the matrix to the chondrocytes
– Because cartilage is avascular, nutrients cannot reach the cells directly via the bloodstream
• Chondrocytes are the cells found in cartilage
– Secrete a gel-like matrix that eventually surrounds and imprisons them
– Also secrete collagen fibers – which form part of this gel-like matrix
– Live in “lacuna” – small depressions in the matrix
Specialized Connective Tissue Includes
Three Kinds of Cartilage
•
The most common type of cartilage is hyaline cartilage
– Covers the ends of bones, allowing them to slide against one another without damage
–
Also found in your nose
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During development, the entire skeleton starts as hyaline cartilage, which then ossifies
• A second kind of cartilage is elastic cartilage
– Forms the outer ear and the epiglottis
• The third kind of cartilage is fibrocartilage
– Its matrix is packed with collagen fibers to provide extra strength
–
Cushions knee joints and the discs between the vertebrae (invertebral discs)
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Specialized Connective Tissue – “Hyaline Cartilage”
Specialized Connective Tissue – “Elastic Cartilage”
Specialized Connective Tissue – “Fibrocartilage”
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Specialized Connective Tissue – “Bone”
• Bone is a hard mineralized tissue found in the skeleton
• Bone cells (osteocytes) secrete an “osteoid substance” that eventually hardens and surrounds the cells in an ossified matrix (solid bone)
– Osteoid substance includes proteins, water, calcium, phosphorous salts
–
After ossification, osteocytes live in lacuna – small depressions in the matrix
– The cells are connected with one another through small channels called canaliculi
Specialized Connective Tissue – “Blood and Lymph”
• Blood and lymph are considered to be fluid connective tissues because their matrix is not a solid
•
• Blood is composed of specialized cells that are carried in the fluid matrix, or plasma
– Blood’s main function is to transport nutrients, gases, hormones, and wastes
Lymph is derived from the interstitial fluid that bathes the cells of the body
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It is collected in the lymphatic vessels
Specialized Connective Tissue – “Blood”
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Specialized Connective Tissue – “Adipose Tissue”
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Adipose tissue contains adipocytes (fat cells) that are specialized for lipid storage
• Adipose tissue does not have an extensive extracellular matrix as do other connective tissues
Muscular Tissue
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•
Muscular tissue provides movement and heat
The function of muscular tissue is to contract
–
Muscle is composed of long cylindrical cells called muscle fibers
– Muscle fibers get shorter when they contract, generating force and often movement
• Muscle is characterized by location, structure, and modes of control
• There are three types of muscular tissue
– Skeletal muscle
– Smooth muscle
– Cardiac muscle
Muscular Tissue – “Skeletal Muscle”
•
• Skeletal muscle tissue makes up the muscles that are attached to our bones
– Highly organized, with multinucleated muscle fibers (muscle cells) lying parallel to each other that are under voluntary control
– Cells contain linear arrays of proteins that create striations that slide past each other, causing contraction
Skeletal muscle moves limbs and stabilizes our trunk
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Muscular Tissue – “Smooth Muscle”
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Smooth muscle lines hollow organs such as the blood vessels and the digestive tract
– Smooth muscle cells are short, cylindrical cells that taper at both ends and have only one nucleus
– Cells are not striated, and are not under voluntary control
Muscular Tissue – “Cardiac Muscle”
• Cardiac muscle contracts to create the heartbeat
•
• Cardiac (heart) muscle has short, branched, striated cells
– Cells have one nucleus and are not under voluntary control
Intercalated discs join neighboring heart cells
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Intercalated discs contain gap junctions, that form tiny channels between cells
– The signal to contract spreads rapidly to all cells through the gap junctions, thus facilitating a coordinated heartbeat
Nervous Tissue
• Nervous tissue responds to the environment by detecting, processing, and coordinating information
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• Nervous tissue contains two categories of cells: neurons and neuroglia
– Neurons are excitable cells that form lines of communication within the nervous system
– Neuroglia are supporting cells of the nervous system
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They improve nutrient flow to the neurons, provide physical support, remove debris, and provide electrical insulation
Central nervous system
– Brain and spinal cord
• Peripheral nervous system
– All other neurons
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Nervous Tissue – “Cells”
Nervous Tissue – “Functions”
• Nerves are clusters of neurons and their projections, sheathed in connective tissue
–
Nerves exist in the body's periphery, and form part of the peripheral nervous system
• The brain and spinal cord contain neurons that receive and integrate information
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These neurons occur in the central axis of the body, and form the central nervous system
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• Sensory nerves conduct sensory messages from the body's sensory organs to the spinal cord, which routes the information to the brain
Motor nerves conduct impulses from the spinal cord to the muscles and glands, which cause muscular movement or glandular secretion
Organ Systems
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• There are 11 organ systems in the human body
– Integumentary - protecting and covering
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Skeletal - support
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Muscular - movement and heat production
– Nervous - sensing and responding
– Cardiovascular - transporting fluids and oxygen
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Respiratory - gas exchange
– Urinary - fluid balance
– Endocrine - regulating sequential growth and development
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Digestive - obtaining nutrients
– Lymphatic - immunity
– Reproductive - continuation of species
Ten of these systems help maintain homeostasis, while the reproductive system maintains the human population
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Body Cavities
• The body has two large cavities, the dorsal and ventral cavities
• Dorsal Cavity
– Includes the cranial cavity housing the brain, and the vertebral cavity which contains the spinal cord
• Ventral Cavity
– Includes the thoracic and abdominopelvic cavities
– The thoracic cavity includes the chest area and houses the heart, lungs, vessels, and lymphatic system
– The abdominopelvic cavity includes
• The abdominal cavity which houses the abdominal organs and is lined with the peritoneum
• The pelvic cavity houses the organs of the urinary system and the reproductive system
Body Cavities
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