Tissues - HOLE’S Essentials of Human Anatomy & Physiology (Chapter 05)

Reticular connective tissue

• Contains thin, reticular fibers
• Fibers form a 3-dimensional network
• Forms a framework for certain internal organs (liver, spleen)
• Referenced under Loose Connective Tissue 2: Reticular connective tissue (Page 40)

Areolar tissue

• See Figure 5.14 (Areolar Tissue) [image caption noted on Page 41]
• Function and location commonly summarized in tables as:
  • Binds organs
  • Located beneath skin, between muscles, beneath epithelial tissues
  • Serves as a general, loose packing tissue with a flexible matrix
• Referenced as Areolar Tissue (Page 41)

Adipose tissue

• Figure 5.15 referenced (Adipose Tissue) [image caption noted on Page 42]
• Function:
  • Protects
  • Insulates
  • Stores fat
• Location:
  • Beneath skin
  • Around kidneys
  • Behind eyeballs
  • On surface of heart

Dense connective tissue

• Characterized by densely packed collagen fibers and a network of elastic fibers
• Contains few cells; most are fibroblasts
• Strength due to collagen fibers; withstands pulling forces
• Poor blood supply; heals slowly
• Locations:
  • Tendons
  • Ligaments
  • Deep layer of skin
  • White layer of the eyeball (sclera)
• Referenced in Page 43

Cartilage

• A rigid connective tissue that:
  • Provides a supportive framework for various structures
  • Protects underlying tissues
  • Serves as models for developing bones
• Lacks a vascular system; heals slowly; cells do not divide often
• Matrix is abundant with collagen fibers in a gel-like ground substance
• Chondrocytes (cartilage cells) lie within lacunae (chambers) in the matrix
• Cartilaginous structures are enclosed within a connective tissue cover called the perichondrium
• The 3 types differ by their type of matrix
• Referenced on Page 45

Three Types of Cartilage

• Hyaline cartilage:
  • The most common type
  • Contains fine collagen fibers in the matrix; appears glassy
  • Found on the ends of bones; supports respiratory structures and passages; important in embryonic development of many bones and bone growth
• Elastic cartilage:
  • Contains elastic fibers in a dense network; flexible
  • Provides framework for the external ears and parts of the larynx
• Fibrocartilage:
  • Tough tissue containing many collagenous fibers
  • Good shock absorber
  • Found in intervertebral discs, knees, and pelvic girdle
• See Page 46 for a summary image set (Hyaloid, Elastic, Fibrocartilage)

Bone (Osseous Tissue)

• The most rigid connective tissue due to mineral salts (calcium salts) in the matrix
• Collagen fibers within the matrix provide some flexibility
• Functions:
  • Supports and protects many body structures in cranial & thoracic cavities
  • Forms sites for muscle attachments
  • Site of blood cell formation (red bone marrow)
  • Stores and releases chemicals, such as calcium and phosphorus
• There are 2 types of bone tissue: compact and spongy
• Compact bone structure:
  • Bone cells (osteocytes) lie within lacunae
  • Matrix arranged in concentric circles (lamellae) around central (Haversian) canals
  • Cylindrical units are osteons (Haversian systems)
  • Central canals contain blood vessels; canaliculi connect cells to the blood supply
• Bone has a good blood supply, enabling rapid recovery after injury
• Referenced on Pages 50–52

Blood

• Functions to transport substances throughout the body
• Transports substances between interior cells and cells exchanging nutrients, gases, and wastes with the environment
• Composed of formed elements suspended in a liquid matrix called plasma
• Formed elements include:
  • Red blood cells (RBCs) to carry oxygen
  • White blood cells (WBCs) for protection against infection
  • Platelets for blood clotting
• Most blood cells are produced by the red bone marrow within certain long bones
• Referenced on Page 53

Summary: Connective Tissues (Table 5.5)

• Loose connective tissue
  • Areolar tissue: Binds organs; Beneath skin, between muscles, beneath epithelial tissues
  • Adipose tissue: Protects, insulates, stores fat; Beneath skin, around kidneys, behind eyeballs, on surface of heart
  • Reticular connective tissue: Supports in walls of liver and spleen
• Dense connective tissue: Binds body parts
  • Tendons, ligaments, deep layer of skin
• Specialized connective tissue
  • Hyaline cartilage: Supports, protects, provides framework; Ends of bones, nose, rings in walls of respiratory passages
  • Elastic cartilage: Supports, protects, provides flexible framework; External ear and parts of larynx
  • Fibrocartilage: Supports, protects, provides framework; Between bony parts of spinal column, parts of pelvic girdle and knee
  • Bone: Supports, protects, absorbs shock; Bones of skeleton
• Blood: Transports substances, helps maintain a stable internal environment; Throughout body within closed system of blood vessels and heart chambers
• Reference: Summary across multiple pages (Pages 55–55)

Connective Tissue Classification (Overview)

• Connective tissue proper
  • Loose connective tissue: Areolar, Adipose, Reticular
  • Dense connective tissue: Dense regular, Dense irregular, Elastic
• Supporting connective tissue
  • Cartilage: Hyaline, Fibrocartilage, Elastic
  • Bone: Compact, Spongy
• Fluid connective tissue
  • Blood
  • Lymph
• Common origin: mesenchyme
• See Page 56 for the schematic breakdown

Types of Membranes (5.4)

• There are 4 types of membranes in the body:
  • 3 types of epithelial membranes
  • 1 type of connective tissue membrane
• Epithelial membranes are thin, sheet-like structures composed of epithelium and connective tissues, covering body surfaces and lining body cavities
• Epithelial membranes types:
  • Serous membranes
  • Mucous membranes
  • Cutaneous membrane
• Connective tissue membranes:
  • Synovial membranes (line joints; composed entirely of connective tissue)
• Referenced on Page 57

Body Membranes (general arrangement)

• Mucous membrane: lines cavities opening to the exterior; contains mucus; epithelium + areolar connective tissue
• Serous membrane: lines closed body cavities; secretes serous fluid; consists of epithelium + connective tissue; has parietal and visceral layers separated by serous fluid
• Cutaneous membrane: skin; dry membrane keratinized for protection and water-proofing
• Synovial membrane: lines joints; secretes synovial fluid; composed of connective tissue
• Visuals show arrangement in the serous cavities (parietal vs visceral) and joint lining (synovial)
• Referenced on Pages 58–59

Types of Epithelial Membranes 1: Serous membranes

• Line cavities that do not open to the outside (thoracic and abdominal cavities)
• Composed of simple squamous epithelium and a layer of areolar connective tissue
• Examples: pleura, pericardium, and peritoneum
• Exist as double-layered membranes:
  • Outer parietal portion lines the cavity wall
  • Inner visceral portion covers the organs
• Contain a small amount of lubricating serous fluid between the 2 layers, secreted by cells of the membrane
• Referenced on Page 59
• Pericardium diagram shows:
  • Fibrous pericardium
  • Serous pericardium (parietal and visceral layers)
  • Pericardial fluid in the cavity
  • Outer balloon wall (parietal serous membrane) and inner balloon wall (visceral serous membrane)
• Visual references: Page 60

Types of Epithelial Membranes 2: Mucous membranes

• Line cavities and tubes that open to the outside of the body
• Consist of epithelium plus a layer of areolar connective tissue
• Contain goblet cells that produce mucus
• Include oral and nasal cavities, and tubular organs of the digestive, respiratory, urinary, and reproductive systems
• Referenced on Page 61

Cutaneous membrane

• The skin
• A dry membrane that is keratinized for protection and water-proofing
• Referenced on Page 61

5.5: Muscle Tissues (Overview)

• General characteristics:
  • Muscle cells (muscle fibers) generate force, contract, and shorten to provide movement
  • 3 types: skeletal, smooth, and cardiac
  • About 40\% of body weight is skeletal muscle, and 10\% is smooth and cardiac muscle
• Referenced on Page 62

Skeletal Muscle Tissue

• Makes up muscles that attach to bones
• Voluntary; can be controlled by conscious effort
• Cells (fibers) are long and cylindrical, striated (striped appearance), with many nuclei
• Cells contract only when stimulated by nerve cells (neurons)
• Functions: move head, trunk, and limbs
• Figure 5.22 (Skeletal Muscle Tissue) and related captions on Page 64

Smooth Muscle Tissue

• Named because cells lack striations
• Cells are spindle-shaped with 1 central nucleus
• Involuntary; cannot be stimulated to contract with conscious effort
• Found in the walls of hollow internal organs (e.g., digestive tract, blood vessels, urinary bladder)
• Figure 5.23 (Smooth Muscle Tissue) on Page 66

Cardiac Muscle Tissue

• Found only in the heart
• Consists of branching cells (fibers), each with a single nucleus
• Cells form branching networks
• Cells are connected by intercalated discs with gap junctions that coordinate impulses between cells
• Involuntary; cannot be controlled by conscious effort
• Striated; has a striped appearance
• Makes up most of the heart and pumps blood through the heart and into blood vessels
• Figure 5.24 (Cardiac Muscle Tissue) on Page 68

Summary: Types of Muscle Tissues (Table 5.6)

• Skeletal muscle tissue (striated): Voluntary movements of skeletal parts; Muscles usually attached to bones
• Smooth muscle tissue (lacks striations): Involuntary movements of internal organs; Walls of hollow internal organs
• Cardiac muscle tissue (striated): Contraction for heart beats; Heart muscle

5.6: Nervous Tissue

• Found in the brain, spinal cord, and nerves
• Neurons (nerve cells):
  • Respond to environmental stimuli or changes by conducting electrical impulses to other neurons, muscles, and glands
  • Components: soma (cell body), dendrites (receive stimuli), and axons (send signals)
  • Functions: Coordinate and regulate body functions
• Neuroglia (nerve glue):
  • Support, nourish, and communicate with neurons
  • Do not conduct impulses
  • Bind nervous tissue together, conduct phagocytosis
• Referenced on Page 70