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Tissues
• Groups of cells similar in structure and function
• The four types of tissues
– Epithelial
• Covers and lines body cavities both inside and outside of the
body.
– Connective
• Protects and insulates vital organs and fills body cavity
spaces. Connects different type of tissues to each other.
– Muscle
• Functions in locomotion, digestive and cardiovascular
functions.
– Nerve
• Communicate electrical impulses which facilitates the action of
both muscles and glands.
Epithelial Tissue
• Covers the entire surface of the body
– Skin and reproductive tracts
• Barriers between what is in and out of the body.
– Lining of the lung, digestive and urinary tracts
• controls what substances enter/exit the body and what
substances stay in/out of the body
• Specialized type types of epithelial tissue include:
– exocrine glands
• secrete substances outside of the body
– (sweat, salivary)
– endocrine glands
• secrete substances (hormones) into the blood
– (insulin, growth hormone)
Epithelial Membranes
• Serous – moist membranes that line internal organs.
Epithelial Membranes
Classification of Epithelial Tissues
Epithelial tissue is classified
based on 2 criteria:
– Shape and number of layers
• Cell shape
– squamous (flattened cells)
• cell width is larger than
cell height
– cuboidal (cube-like cells)
• cell width is equal to
cell height
– columnar (column-like
cells)
• cell height is larger than
cell width
Classification of Epithelial Tissues
• Number of layers of
epithelial cells
– Simple
• Thin layer allows for
exchange of
substances into or
out of the body
– Stratified
• Multiple layers
protects act as a
natural barrier to
prevent abrasion,
puncture.
Epithelia: Simple Squamous
Figure 4.2a
Epithelia: Simple Cuboidal
• Single layer of cubelike cells with large,
spherical central nuclei
• Function in secretion and absorption
• Present in kidney tubules, ducts and
secretory portions of small glands, and
ovary surface
Figure 4.2b
Epithelia: Simple Columnar
Figure 4.2c
Epithelia: Pseudostratified
Columnar
• Single layer of cells with different heights;
some do not reach the free surface
• Nuclei are seen at different layers
• Function in secretion and propulsion of
mucus
• Present in the male sperm-carrying ducts
(nonciliated) and trachea (ciliated)
Figure 4.2d
Epithelia: Stratified Squamous
• Thick membrane composed of several
layers of cells
• Function in protection of underlying areas
subjected to abrasion
• Forms the external part of the skin’s
epidermis (keratinized cells), and linings of
the esophagus, mouth, and vagina
(nonkeratinized cells)
Figure 4.2e
Epithelia: Transitional
• Several cell layers, basal cells are
cuboidal, surface cells are dome shaped
• Stretches to permit the distension of the
urinary bladder
• Lines the urinary bladder, ureters, and part
of the urethra
Figure 4.2f
Connective Tissue
• Widely spaced cells separated by fibers and ground substance. Most
abundant and variable tissue type
– Connective tissue proper
– Dense
» Regular and Irregular
– Loose
» Areolar, Adipose, Reticular.
– Cartilage
• Hyaline, Elastic, Fibrocartilage
– Bone
• Spongy, Compact
– Blood
• Fluid connective tissue (plasma ) red blood cells, white blood cells,
platelets
• Functions
– connects organs
– gives support and protection (physical and immune)
– stores energy and produces heat
– movement and transport of materials
Connective Tissue
Figure 4.5
Structural Elements of Connective Tissue
Cells of Connective Tissue
• Fibroblasts produce fibers and ground substance
–
–
–
–
Adipocytes store triglycerides
Chondroblasts – produce cartilage
Osteoblasts – build bone
Hematopoietic stem cells – blood
• White blood cells, plasma cells, macrophages, and mast cells
Fibers of Connective Tissue
• Collagen fibers (white fibers)
– tough, stretch resistant, yet flexible
• tendons, ligaments and deep layer of the skin
• Reticular fibers
– thin, collagen fibers coated with glycoprotein
• framework in spleen and lymph nodes
• Elastic fibers (yellow fibers)
– thin branching fibers of elastin protein
– stretch and recoil like rubberband (elasticity)
• skin, lungs and arteries stretch and recoil
Connective Tissue Ground Substance
• Gelatinous material
between cells
– absorbs
compressive
forces
– attract sodium
and hold water
Ground Substance:
Proteoglycan Structure
Figure 4.6b
Fibrous Connective Tissue Types
• Loose connective tissue
– gel-like ground substance between cells
– types
• areolar
• reticular
• adipose
• Dense connective tissue
– fibers fill spaces between cells
– types vary in fiber orientation
• dense regular connective tissue
• dense irregular connective tissue
Loose Connective Tissue Proper: Areolar
Areolar Connective Tissue
Figure 4.8b
Connective Tissue: Embryonic
Figure 4.8a
Adipose Connective Tissue
Reticular Connective Tissue
Figure 4.8d
Connective Tissue: Dense Regular
Figure 4.8e
Connective Tissue : Dense Irregular
Figure 4.8f
Connective Tissue: Hyaline Cartilage
Figure 4.8g
Connective Tissue: Elastic Cartilage
• Similar to hyaline cartilage but with more
elastic fibers
• Maintains shape and structure while
allowing flexibility
• Supports external ear (pinna) and the
epiglottis
Figure 4.8h
Connective Tissue: Fibrocartilage
Cartilage
• Matrix similar to hyaline cartilage but less
firm with thick collagen fibers
• Provides tensile strength and absorbs
compression shock
• Found in intervertebral discs, the pubic
symphysis, and in discs of the knee joint
Figure 4.8i
Connective Tissue: Bone
Figure 4.8j
Connective Tissue: Blood
Figure 4.8k
Nervous Tissue
Figure 4.10
Muscle Tissue: Skeletal
• Long, cylindrical, multinucleate cells with
obvious striations
• Initiates and controls voluntary movement
• Found in skeletal muscles that attach to
bones or skin
Figure 4.11a
Muscle Tissue: Cardiac
• Branching, striated, uninucleate cells
interdigitating at intercalated discs
• Propels blood into the circulation
• Found in the walls of the heart
Figure 4.11b
Muscle Tissue: Smooth
Figure 4.11c
Tissue Shrinkage and Death
• Atrophy = loss of cell size or number
– disuse atrophy from lack of use (leg in a cast)
• Necrosis = pathological death of tissue
– gangrene - insufficient blood supply
• Diabetic complications.
– infarction - death of tissue from lack of blood
• Heart attack or cerebral vascular accident ( stroke)
– decubitus ulcer - bed sore or pressure sore
• Pressure cuts off blood supply to a specific part of body.
• Diabetic Ulcer
Bedsores