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

Figure 4.2b

• 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

Epithelia: Simple Columnar

Figure 4.2c

Epithelia: Pseudostratified Columnar

Figure 4.2d

• 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)

Epithelia: Stratified Squamous

Figure 4.2e

• 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)

Epithelia: Transitional

Figure 4.2f

• 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

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

Figure 4.8h

• Similar to hyaline cartilage but with more elastic fibers

• Maintains shape and structure while allowing flexibility

• Supports external ear (pinna) and the epiglottis

Connective Tissue: Fibrocartilage Cartilage

Figure 4.8i

• 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

Connective Tissue: Bone

Figure 4.8j

Connective Tissue: Blood

Figure 4.8k

Nervous Tissue

Figure 4.10

Muscle Tissue: Skeletal

Figure 4.11a

• Long, cylindrical, multinucleate cells with obvious striations

• Initiates and controls voluntary movement

• Found in skeletal muscles that attach to bones or skin

Muscle Tissue: Cardiac

Figure 4.11b

• Branching, striated, uninucleate cells interdigitating at intercalated discs

• Propels blood into the circulation

• Found in the walls of the heart

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