Download Connective Tissue and More Connective tissues, nervous, and muscle tissues

Connective Tissue and More Connective tissues, nervous, and muscle tissues

What is connective tissue?

Connective tissues 

Represent the most abundant by weight and most widely distributed type of tissue in the body



Generally: Bind structures together Fill spaces in the body Examples: Connective tissue proper, Cartilage, Bone, Blood



Connective Tissue

Figure 4.6

Connective Tissues – general functions Connect epithelium to the rest of the body (basal lamina)  Have no contact with environment (usually covered by epithelium)  Usually highly vascular (good blood supply)  Also: 

   

Protect delicate organs Provide structure and support (bone) Insulate and store energy (fat) Transport materials (blood)

Characteristics of Connective Tissues  

Specialized cells Solid extracellular protein fibers 



Collagen, elastic, and reticular

Fluid extracellular ground substance 

unstructured material that fills the space between cells

These latter two extracellular features are called Matrix

The Matrix 

The extracellular components of connective tissues (fibers and ground substance):  



Makes up the majority of tissue volume Determines specialized function:

connective tissue proper  syrupy liquid   

cartilage  gel-like matrix blood  fluid matrix bone  crystalline solid

Matrix: ground substance  



Fills the spaces between cells and fibers Functions as a molecular sieve through which nutrients diffuse between blood capillaries and cells Composed of 





interstitial fluid Cell adhesion proteins: serve as glue for cells to attach to matrix Proteoglycans: consist of a protein core with glycosaminoglycans (GAGs) such as chondroitin sulfate and hyaluronic acid which trap water and determine the consistency

Ground Substance: Proteoglycan Structure

Figure 4.7

Matrix: Protein Fibers 





Collagen – tough but inelastic; provides very high tensile strength (greater than steel) Elastic – long, thin fibers that allow for stretch; composed of elastin which is similar to collagen Reticular – branched collagenous fibers that form delicate networks, resist force in many directions

Elastic fibers allow a tissue to stretch

Cells 

  



Fibroblasts – connective tissue proper Chondroblasts – cartilage Osteoblasts – bone Hematopoietic stem cells – blood White blood cells, plasma cells, macrophages, and mast cells

Other CTP cell types Melanocytes  Adipocytes – fat cells; insulation, energy, 

padding 

Mesenchymal cells – stem cells; can differentiate into other mesodermal cell types

Fibroblasts 



Stationary in the tissue Secrete the protein fibers and ground substance found in the matrix

Classification of Connective Tissues 

Connective tissue proper: 



Fluid connective tissues: 



connect and protect transport

Supporting connective tissues: 

structural strength

Classification of connective tissues

Connective tissue proper (CTP) 



Contains many types of cells and extracellular fibers in a syrupy ground substance Look at the cell types and the number and types of fibers to identify the type of tissue

Categories of Connective Tissue Proper 

Loose connective tissue:  



more ground substance, less fibers e.g., fat (adipose tissue)

Dense connective tissue:  

more fibers, less ground substance e.g., tendons

CTP: 3 types of Loose Connective Tissues Proper   



The “packing materials” of the body Packing material, fills spaces Contains mesenchyme cells – leftover from development, can differentiate into many of the other resident cell types 3 types in adults:   

areolar adipose reticular

Connective Tissue: Embryonic 

Mesenchyme – embryonic connective tissue 

 

Gel-like ground substance with fibers and starshaped mesenchymal cells Gives rise to all other connective tissues Found in the embryo

Loose CTP #1: Areolar 

Areolar connective tissue      



Least specialized, open framework Viscous ground substance with all three connective tissue fibers Fibroblasts, macrophages, mast cells, and some white blood cells Wraps and cushions organs Widely distributed throughout the body Separates skin from deeper tissues Holds blood vessels and capillary beds:

Areolar Connective Tissue Model

Figure 4.8

Loose CTP #1: Areolar

Figure 4.9a

Loose CTP #2: Adipose 

Adipose connective tissue 







Matrix similar to areolar connective tissue with closely packed adipocytes Reserves food stores, insulates against heat loss, and supports and protects Found under skin, around kidneys, within abdomen, and in breasts Local fat deposits serve nutrient needs of highly active organs

Loose CTP #2: Adipose

Figure 4.9b

Loose CTP #2: Adipose 

Contains many adipocytes (fat cells)

Figure 4–10a

Adipose Cells 

Adipocytes in adults do not divide:  



expand to store fat shrink as fats are released

Mesenchymal cells divide and differentiate:  

to produce more fat cells when more storage is needed

Loose CTP #3: Reticular 

Reticular connective tissue   



Loose ground substance with reticular fibers Reticular cells lie in a fiber network Forms a soft internal skeleton, or stroma, that supports other cell types Found in Reticular organs: lymph nodes, bone marrow, liver, and the spleen

Loose CTP #3: Reticular

Figure 4.9c

Loose CTP #3: Reticular 

Provides support

Figure 4–10b

CTP: 3 Types of Dense Connective Tissues 



Connective tissues proper Tightly packed with high numbers of collagen or elastic fibers:   

dense regular connective tissue dense irregular connective tissue elastic tissue

Dense CTP #1: Dense Regular 

Dense Regular Connective Tissue   



Parallel collagen fibers with a few elastic fibers Major cell type is fibroblasts Attaches muscles to bone or to other muscles, and bone to bone Found in tendons, ligaments, and aponeuroses

Dense CTP #1: Dense Regular

Figure 4.9d

Dense CT #1: Dense Regular  

e.g. tendons, ligaments Attachment and stabilization

Dense CTP #2: Dense Irregular 

Dense Irregular Connective Tissue 

 



Irregularly arranged collagen fibers with some elastic fibers Major cell type is fibroblasts Withstands tension in many directions providing structural strength Found in the dermis, periosteum, perichondrium, submucosa of the digestive tract, and fibrous organ capsules

Dense CTP #2: Dense Irregular

Figure 4.9e

Dense CT #2: Dense Irregular

Dense CT #3: Elastic Tissue 

Made of mostly elastic fibers (elastin): 

e.g., elastic ligaments of spinal vertebrae

Figure 4–11c

Dense CT #3: Elastic Tissue

Fluid Connective Tissues 



Fluid connective tissues: blood and lymph  

watery matrix of dissolved proteins carry specific cell types (formed elements)

Fluid CT: Blood  

Formed elements Formed elements are the cells plus the platelets (which aren’t technically cells) =   

Red blood cells (erythrocytes) = majority White blood cells (leukocytes) Platelets

Connective Tissue: Blood 

 

Red and white cells in a fluid matrix (plasma) Contained within blood vessels Functions in the transport of respiratory gases, nutrients, and wastes

Fluid Elements of Blood 

Extracellular:   

Plasma – fluid portion of blood Interstitial fluid – squeezed out of capillaries Lymph – Int. fluid entering lymph vessels

Connective Tissue: Blood

Figure 4.9j

Flow of body fluids – A Cycle 

  

Plasma in blood (without formed elements) squeezes out of capillaries due to blood pressure and small spaces between some epithelial cells Now in tissue spaces it is called interstitial fluid. Passively enters lymphatic system. Now it is called lymph. Returns to blood through subclavian veins then to heart Cycle repeats

Supporting Connective Tissues Bone and Cartilage

What do supporting connective tissues do?

Supportive Connective Tissues 



Function: Support soft tissues and body weight Types: 

cartilage:  



gel-type ground substance for shock absorption and protection

bone: 



calcified (made rigid by calcium salts, minerals) for weight support

Supporting CT #1: Cartilage Matrix:  Proteoglycans derived from chondroitin sulfates (polysaccharide) makes it gel-like  Different cartilage types derive their properties from the number and type of proteoglycans and the number and type of protein fibers Cells:  chondrocytes, surrounded by lacunae (chambers)  chondroblasts (progenitor of chondrocytes)

Cartilage Structure 

No blood vessels: 



chondrocytes produce antiangiogenesis factor

Perichondrium (a dense irregular CTP):  

outer, fibrous layer (for strength) inner, cellular layer (for growth and maintenance)

Cartilage Growth - Interstitial 

Interstitial growth (inside-out) by chondrocytes

Figure 4–13a

Cartilage Growth - Appositional 

Appositional growth (adding to the outside) [Adults]

Figure 4–13b

The 3 Types of Cartilage 

Hyaline (glass) cartilage:    



Elastic cartilage: 

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most common translucent matrix, packed collagen no prominent fibers joint perichondrium tightly packed elastic fibers

Fibrocartilage: 



very dense collagen fibers joint pads

Connective Tissue: Hyaline Cartilage     

Amorphous, firm matrix with imperceptible (clear) network of collagen fibers Chondrocytes lie in lacunae Supports, reinforces, cushions, and resists compression Forms the costal cartilage (ribs) Found in embryonic skeleton, the ends of long bones, nose, trachea, and larynx

Connective Tissue: Hyaline Cartilage

Figure 4.9f

Hyaline Cartilage 

Reduces friction in joints 

Cover the end of long bones

Figure 4–14a

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 May be stacked up

Connective Tissue: Elastic Cartilage

Figure 4.9g

Elastic Cartilage 

Flexible support 

found in external ear and epiglottis

Figure 4–14b

Connective Tissue: Fibrocartilage 





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: Fibrocartilage

Figure 4.9h

Fibrocartilage

Joints 

Most joints have both hyaline cartilage and fibrocartilage in them

Connective Tissue: Bone (Osseous Tissue) 



Hard, calcified matrix with flexible collagen fibers found in bone Osteocytes are found in lacunae and are well vascularized:  

 



arranged around central canals within matrix small channels through matrix (canaliculi) access blood supply (no diffusion through matrix)

Supports, protects, and provides levers for muscular action Stores calcium, minerals, and fat Marrow inside bones is the site of hematopoiesis

Connective Tissue: Bone

Figure 4.9i

Bone 



Very little ground substance matrix is 2/3 Calcium salts (phosphate, carbonate), 1/3 collagen

Bone: what to look for      

Osteon (whole circular structure) Concentric lamellae (of matrix) Central canal (at center of lamellae) Osteoblasts Osteocytes in lacunae Canaliculi – canals for diffusion

Close Up: ostocyte and canaliculi 

Cytoplasmic extensions

Bone growth 



Appositional only (outside) Osteocytes secrete matrix fibers and calcium salts, forms concentric rings

Comparing Cartilage and Bone

Table 4–2

Nervous Tissue 

Also called neural or nerve tissue: 

   

Branched neurons with long cellular processes and support cells specialized for conducting electrical impulses rapidly senses internal or external environment process information and controls responses Found in the brain, spinal cord, and peripheral nerves

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

3 Types of Muscle Tissue 

Skeletal muscle: 



Cardiac muscle: 



large body muscles responsible for movement found only in the heart

Smooth muscle: 

found in walls of hollow, contracting organs (blood vessels; urinary bladder; respiratory, digestive and reproductive tracts)

Muscle Tissue: Skeletal

Figure 4.11a

Muscle Tissue: Cardiac 

 

Branching, striated, uninucleate cells interlocking at intercalated discs Propels blood into the circulation Found in the walls of the heart

Muscle Tissue: Cardiac

Figure 4.11b

Muscle Tissue: Smooth 





Sheets of spindle-shaped cells with central nuclei that have no striations Propels substances along internal passageways (i.e., peristalsis) Found in the walls of hollow organs

Muscle Tissue: Smooth

Figure 4.11c

Developmental Aspects 

Primary germ layers: ectoderm, mesoderm, and endoderm 





Three layers of cells formed early in embryonic development Specialize to form the four primary tissues

Nerve tissue arises from ectoderm

Developmental Aspects 

 

Muscle, connective tissue, endothelium, and mesothelium arise from mesoderm Most mucosae arise from endoderm Epithelial tissues arise from all three germ layers

Body Membranes 

Membranes: 

 

are physical barriers that line or cover portions of the body

Consist of an epithelium Always supported by connective tissues

4 Types of Membranes 1. 2. 3. 4.

Mucous Serous Cutaneous Synovial

Figure 4–16

Mucous Membrane 

Mucous membranes (mucosae): 





Epithelial surfaces must be moist:  



line passageways that have external connections: digestive, respiratory, urinary, and reproductive tracts Goblet cells secrete mucins  mucus to reduce friction to facilitate absorption and excretion

Lamina propria: 

is areolar tissue

Structure of Mucous Membrane

Figure 4–16a

Serous Membranes 

 

Line cavities not open to the outside; sealed internal subdivisions of ventral body cavity, e.g. peritoneum Are thin and transparent but strong Have fluid transudate to reduce friction

Epithelial part = Mesothelium (simple squamous) Connective tissue part = areolar tissue

Structure of Serous Membrane

Figure 4–16b

Serous Membranes

Figure 4.12c

Double Membranes 

Serous membranes:  



have a parietal (wall) portion covering the cavity and a visceral portion (serosa) covering the organs

Serous membranes: 

consist of parietal layer and visceral layer

Cutaneous Membrane 

Cutaneous membrane:   

is skin, surface of the body thick, waterproof, and dry Made up of epidermis and dermis (papillary and reticular layers). What types of tissues?

Structure of Cutaneous Membrane

Figure 4–16c

Synovial Membranes 





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Line articulating (moving) joint cavities Produce synovial fluid (lubricant, nutrients to chondrocytes of articular cartilage) Protect the ends of bones (which themselves are covered in what?) Lack a true epithelium (incomplete, no basal lamina)

Structure of Synovial Membranes

Figure 4–16d

Summary: Inflammation and Regeneration

Figure 4–20

Aging Epithelia get thinner  CT more fragile So bruise easily, bones more brittle 

Different PGs made by chondrocytes

Proteoglycans

Summary 

  

  

Connective tissues – structures and functions CTP (loose, dense) Fluid (blood, lymph) Supporting (cartilage, bone) Nervous tissue – brief overview Muscle tissue overview (3 types) Membranes (4 types)