TissuesChapter 5

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4 Types of TissuesAll tissues can be classified into four major

categories based on structure and function:1. Epithelial: Covers and protect body surfaces, lines

body cavities, moves substances in and out of blood (secretion, excretion & absorption), form glands

2. Connective: support, connection, transport, protection

3. Muscle: moves the body & its parts; specialized for contractility

4. Nervous: provides communication between body parts and coordinates body functions

Embryonic Development• Zygote becomes a blastocyst

through mitotic division • Cells of the blastocyst regroup into

primary germ layers– Endoderm, mesoderm, ectoderm– Gastrulation: process of blastocyst

differentiating into 3 germ layers– Histogenesis: process of germ layers

differentiating into diff tissues

Epithelial TissueSubdivided into 2 types:1. Membranous

– Covers the body & some of its parts – Lines body cavities (pleural,

pericardial, peritoneal), blood vessels, respiratory, digestive and genitourinary tracts

2. Glandular – Form the secretion units of the

endocrine & exocrine glands

Epithelial TissueFunctions of epithelial tissues:1. Protection

– Ex: skin protects body from injury & disease-causing micro-organisms

2. Sensory– Epithelial structures that specialize in sensory functions

found in skin, nose, eye, ear

3. Secretion– Glandular epithelium secrete hormones, digestive juices &

sweat

4. Absorption– Ex: gut absorbs nutrients; exchange of respiratory gases

5. Excretion – Ex: kidney tubules concentrate & excrete urine and other

waste products

Epithelial Tissue• Basement membrane

– Thin, noncellular layer of adhesive– Connects epithelial tissue and

underlying connective tissue • Avascular

– “without” vascular– Epithelial cells do not have blood vessels– Oxygen & nutrients diffuse from

capillaries through connective tissue & basement membrane to epithelial cells

Classification of Membranous Epithelial Tissue

• Cell Shape– Squamous: flat, plate-like– Cuboidal: cube-shaped; larger cytoplasm– Columnar: narrow and cylinder-shaped– Pseudostratified: single-layered; all cells

touch the basement membrane but may not extend to the top of the membrane

• Layers of Cells– Simple: single layer– Stratified: cells are layered on top of one

another– Transitional: cell shape & layers differ

Founds in areas where diffusion or filtration are necessary

Examples of locations:

•Alveoli (air sacs)

•Linings of blood & lymphatic vessels

•Surfaces of pleura, pericardium & peritoneum

Examples of locations:

•Glands and their ducts

Examples of Locations:

•Mucous membranes such as stomach, intestine, uterus

Goblet cells (produce mucous) & microvilli (increase surface area) are usually found on these cell types

Examples of locations:

•Respiratory tract, male urethra

Goblet cells & cilia present

Examples of locations:

•Skin

Keratin (tough protein) provides (fig 5-8 – not pictured)

Examples of locations:

•Areas subject to stress and tension changes (Urinary bladder)

Glandular Epithelium

• Specialized for secretory activity• Unicellular glands

– Single celled– Ex: goblet cells

• Multicellular glands– Function in clusters, solid cords or

specialized follicles

Endocrine vs Exocrine

• All glands are classified as endocrine or exocrine

• Exocrine glands– Discharge/secrete into ducts– Ex: salivary glands

• Endocrine glands– “ductless glands”– Secrete hormones directly into blood or

interstitial fluid– Ex: pituitary and thyroid glands

Structural Classification of Exocrine Glands

• (Table 5-2, p. 133)• Shape of gland:

– Tubular– Alveolar (sac-like)

• Complexity of gland:– Simple (one duct)– Compound – > 2 ducts (branched)

Functional Classification of Exocrine Glands

1. Apocrine– Collect secretory products at apex (tip)– Apex of cell pinches off – Cell repairs itself & repeats process– Ex: milk-producing mammary glands

2. Holocrine– Collect secretory product inside the cell– Rupture to release (self-destructs)– Ex: sebaceous glands (oil glands)

3. Merocrine– Discharge through plasma membrane– This type applies to most exocrine glands– Ex: salivary glands

Figure 5-12, p. 132

Connective Tissue

• Most widespread tissue in the body• Functions:

– Connection– Support – Transport– Protection– Insulation

Characteristics of Connective Tissue

• Common origin – mesoderm• Matrix

– Intercellular material– Few cells, fibers, fluid, ground

substance (material between cells)– Fibers:

1. Collagenous fibers2. Reticular fibers3. Elastic fibers

Fibers1. Collagenous fibers

– “white fibers”– Made of collagen (fibrous protein)– Tough, strong

2. Reticular fibers– Delicate– Reticulin – protein– Support small structures (ex: capillaries)

3. Elastic fibers– Extensible & elastic– Elastin – protein– Found in “stretchy” tissue (ex: cartilage of the

external ear)

Classification of Connective Tissue

1. Fibrous– Loose (areolar)– Adipose– Reticular– dense

2. Bone3. Cartilage

– Hyaline– Fibrocartilage– elastic

4. Blood

**Reference Table 5-3, pp. 134-135**

Fibrous Connective Tissue1. Loose connective (areolar) tissue (fig 5-13)

– Stretchable– most abundant connective tissue in the

body– Connects adjacent structures

• Ex: btwn other tissues and organs• Ex: superficial fascia

Fibrous Connective Tissue2. Adipose tissue (fig 5-14)

– Contains mainly fat cells– Supportive/protection pads around kidneys

& other body structures– Storage deposit for excess food– Insulating material, conserves body heat

Fibrous Connective Tissue3. Reticular Tissue (Fig 5-16)

– 3D web of reticular fibers– Forms the framework of the spleen,

lymph nodes & bone marrow– Meshwork filters harmful substances out

of the blood

Fibrous Connective Tissue4. Dense Fibrous Tissue (fig 5-17, 5-18, 5-19)• Densely packed fibers• Regular Dense CT

– Fibers arranged in regular, parallel rows– Collagen fibers– Flexible, strong– Tendons (muscle to bone) & ligaments (bone to bone)

• Irregular Dense CT– Fibers intertwine – Withstand stress from any direction– Ex: dermis (inner layer of skin); outer capsule of kidney &

spleen

Bone Tissue

• We will cover this when we cover the skeletal system

• Just know that bone is a type of connective tissue

Cartilage

• Only 1 cell type – chondrocyte– Located in lacuna

• Avascular – receive nutrients via diffusion

• Injuries to cartilage heal slowly due to poor nutrient delivery

Cartilage - Types1. Hyaline cartilage

– Most common– Covers ends of long bones (where joints

articulate)– Found in supporting rings of respiratory tubes

2. Fibrocartilage– Strongest, most durable– Intervertebral disks– Menisci in knee joint

3. Elastic cartilage– Fine elastic fibers– High degree of flexibility– External ear

Blood• Unusual type of connective tissue• No ground substance• Matrix = plasma (55%)• Formed elements = blood cells (45%)

– Erythrocytes – RBCs– Leukocytes – WBCs– Thrombocytes – platelets

• Transport function– Respiratory gases, nutrients, waste

products

Muscle Tissue

3 types:– Skeletal muscle tissue– Smooth muscle tissue– Cardiac muscle tissue

Skeletal Muscle Tissue• Muscles (attached to bone)• “striated voluntary” muscle

• Structure: striations, multi-nucleated, long, tread-like cells, bundles of microfilaments

Smooth Muscle Tissue• Aka: visceral muscle tissue• Lines walls of hollow internal organs

(viscera)– Stomach, intestines, blood vessels

• “non-striated involuntary” muscle

• Structure: long, narrow cells, non-striated

Smooth Muscle Tissue

Cardiac Muscle Tissue• Walls of the heart• “striated involuntary” muscle

• Structure: striations, dark band (intercalated disks (where plasma membranes meet up)

Nervous Tissue• Rapidly integrates activities of

various parts of the body• Rapid communication is made

possible b/c of the excitability & conductivity characteristics of the nervous tissue

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Nervous System

3 Parts:• Brain• Spinal cord• Nerves

Nervous Tissue:• Common origin:

ectoderm• Two cell types:

1. Neurons (nerve cell)2. Neuroglia (supporting

cells)

Anatomy of Neurons• Cell body –

soma• Cell processes:

– Axon transmits nerve impulses away from cell body

– Dendrites carry signals towards axon

http://www.nida.nih.gov/jsp/MOD3/images/NEURON2.gif

Tissue Repair

After mechanical damage or tissue injury:

• Phagocytic cells remove dead or injured cells

• Regeneration: growth of functional new tissue (via mitotic division)

Repair capacity based on tissue type

Epithelial & Connective Tissue Repair

• Greatest capacity to regenerateEpithelial Tissue:

– Cut/injury cell division tissue regeneration

Connective Tissue:– Cut/injury activation of cells that make

collagen fibers injury site filled w/ dense fibrous CT

Small injury – dense fibrous CT replaced by normal tissue

Deep/large injury – dense fibrous CT forms scar

Muscle Tissue Repair

• Limited repair capacity• Damaged muscle tissue replaced

with fibrous CT• Results in loss of some or all ability

to function normally

Nervous Tissue Repair

• Limited ability to regenerate• Some neurons outside the brain and

spinal cord can regenerate (slow process)

• Majority of the time: brain & spinal injuries always result in permanent damage

Body Membranes

• Membrane – thin, sheet-like structure• Two types:

– Epithelial membranes• Composed of epithelial tissue and

underlying connective tissue

– Connective Tissues membranes• Composed entirely of connective tissue

Epithelial Membranes1. Cutaneous membrane

– Cover body surfaces exposed to external environment (skin)

2. Serous membrane– Single membrane covering two different

surfaces• Parietal membrane – lines walls of body cavities• Visceral membrane – covers surface of organs

– Secrete thin, watery substance to prevent rubbing

3. Mucous membrane– Line body surfaces open to exterior

• Ex: respiratory, digestive, urinary & reproductive tracts

Connective Tissue Membranes

Synovial membranes• Lines spaces between bones & joints• Secrete thick, colorless, lubricating

fluid (synovial fluid)• Fluid helps reduce friction btwn bone

surfaces

Mechanisms of Disease – Tumors & Cancer

• Neoplasm – “new matter” (tumor)– Abnormal growth of cells

• Benign Tumors– Do no spread to other tissues– Slow growth– Encapsulated– Usually not lethal unless interfere w/ organs

Mechanisms of Disease – Tumors & Cancer

• Malignant tumors (cancer)– Not encapsulated– Spreads (metastasizes) – Cancer cells spread via blood or

lymphatic system– Rapid growth/spread to nearby tissue

(Known) Causes of Cancer• Genetic Factors

– Inherited cancer genes “oncogenes”– Tumor suppressor gene – fails to operate– Usually genetic predisposition coupled with cancer-

causing mechanisms• Ex: breast cancer

• Carcinogens (cancer markers)– Affect genetic activity abnormal cell reproduction– Also called mutagens– Ex: chemicals, sun, viruses

• Age– Some cancers arise based on age

• Ex: leukemia (young) & colon cancer (older adults)

Detection of Cancer• Self-examination

– Breast and testicular exams• Medical Imagining

– X-ray • Ex: mammogram – detection of breast cancer

– CT, MRI, ultrasound• Produce cross-section of body images for tumor

detection

• Blood tests– Look for tumor markers (ex: PSA)

• Biopsy– Removal of tumor tissue

Cancer Treatment Options• Stage and grade cancer

– Helps determine outcomes

• Surgical removal (if possible)– Could leave behind malignant cells

• Chemotherapy – cytotoxic (cell-killing) drugs– Destroys remaining malignant cells

• Radiation therapy– Destructive x-ray or gamma radiation destroys

cancer cells

• Immunotherapy– Boosting immune system again viruses

Anthony’s Textbook of Anatomy and Physiology 17th Edition. Thibodeau, Gary A. PhD and Patton, Kevin T. PhD. Mosby, Inc.