Histology Unit Flashcards
Explain the Embryonic origin of tissues
Following fertilization, the zygote produces many cells to create an embryo (a more developed version of itself before the fetus). These first few cells possess the ability to form into varied, specialized cells. This creates the three germ layers from which the tissues and organs originate and form from.
(Superficial) Ectoderm: Skin, neuron, pigment
(Middle) Mesoderm: Cardiac, skeletal, smooth, red blood cells
(Deep) Endoderm: Lung, Thyroid, pancreatic
EPITHELIAL ARE FOUND IN ALL 3
NEURONS ARE FOUND ON SURFACE
MOST MUSCLE AND CONNECTIVE TISSUE ARE IN MESODERM
Describe the two tissue membranes of the body
The two tissue membranes of the body are the epithelial tissue membranes and the connective tissue membranes. Each are responsible for lining or acting as a cover for the body. Connective tissue membranes consist of only connective tissue. They are found encapsulating an organ or lining the cavities of a joint. The epithelial membrane is composed of an epithelial layer attached to a layer of connective tissue.
Connective: Synovial membranes (joint)
Epithelial: Mucous Membranes (digestive, respiratory, urinary, & reproductive tracts), Serous membranes (body cavities), Cutaneous membranes (Skin)
Explain the characteristics and functions of muscle tissue
- High Vascularity: equire a significant supply of oxygen and nutrients to support their metabolic demands during contraction and recovery
- High cellularity: facilitate their specific functions, such as contraction and force generation
- Multinucleated and long
- CELL: Myoblasts –> Myocytes (fibers- arranged in layers and bundles in tissues)
- Sarcomere - basic contractile unit within myoctyes (Contains organized arrangements of actin (thin) and myosin (thick) protein filaments) These allow the muscle tissues to contract
- Repeating arrangements of sarcomeres create striations - Organized, structured
- Voluntary muscle tissue contain more striations because they need more sarcomeres (contractile units) to create more contractions to produce more force and power
name and describe the three types of muscle tissue
- Skeletal Muscle: Voluntary; Body movement (bones), multinucleated - more energy, striated, cylindrical, ex. biceps, quadricepts
- Smooth Muscle: Lacks striations, walls of internal organs, involuntary - ANS, spindle-shaped, single nucleus, doesn’t require energy
- Cardiac Muscle: contractile walls of heart, one nucleus, contains striations - needs to contract in order to pump blood for the body, involuntary - intrinsic rhythm, intercalated discs - junctions that connect heart muscle cells, are synchronized to resist pressures, Cell: Cardiomyocytes
What are the characteristics of connective tissues?
- Same Origin: Embryonic tissue - Mesenchyme
- Extracellular matrix (complex network- fibers, ground substance: contains nutrients & wastes, cells)
Name and describe the fibers found in connective tissues
- Collagen: tough- bundled structure, high tensile-strength: can bend and stretch even under a lot of stress
- Elastic: Long, thin; rubber qualities-recoil and stretch
- Reticular: collagenous; extensive branches-structural support, surrounds cells & tissues
What are the four types of connective tissue?
- Proper
- Cartilage
- Bone
- Blood
What are the classes of connective proper tissue?
- Loose (Areolar, Reticular, Adipose)
- Dense (Elastic, Irregular, Regular)
Explain Areolar tissue
- MOST widely distributed
- Supportive framework Connects skin to underlying organs/muscle
- Fills spaces between muscles
- Can soak up excess fluid - large ground substance
- Locations: Around organs, between muscles,
Describe the characteristics of connective proper tissue
- Made out of fibroblasts (developing) and fibrocytes (mature)
- Classes: Areolar, Reticular, Adipose
Explain Adipose Tissue
- High vascularity - deliver nutrients to adipocytes, mobilize stored fat into bloodstream for immediate energy use, insulation-heat distribution throughout body
- NO visible matrix: dominance- tissue primarily contains fat cells, smaller extracellular matrix, adipocytes are tightly packed together, large lipid deposits shift nuclei
- Made up of adipocytes
- Functions: Insulation, Protection of organs, site of fuel storage
- Locations: beneath skin; around kidneys, eyes, abdominal area, and breasts
Explain Reticular Tissue
- Delicate matrix: network of thin fibers and fibroblasts
- Branches support free blood cells
- Forms stroma by supporting lymphocytes (lymph nodes, spleen, bone marrow)- supportive tissue; composed of connective tissue, blood vessels, nerves
- Looks like a Sakura blossom tree
Explain Dense Regular tissue
- Tightly packed bundles of collagen fibers running in same direction
- Poor vascularity
- Mainly composed of fibroblasts
- locations: Tendons (Muscles to bones), Aponeuroses (Muscles to muscles, muscles to bones), ligaments (bones to bones)
Explain dense irregular tissue
- even thicker bundles of collagen fibers
- runs in zigzag lines, resist tension in many directions: Flexibility & strength of skin, surrounds & stabilizes joints, organ capsules such as outer layer of heart
- Locations: dermis of skin, fibrous joint, organ capsules, aorta
- Provides strength & durability, gives support by forming capsules around organs/structures, flexibility
Explain characteristics and classes of cartilage connective tissue
- Cells are chondrocytes
- Lacks blood vessels - avascularity
- No nerve fibers
- Large amounts of tissue fluid
- Withstands tension and pressure: High water content (distributes pressure, provides cushion), collagen arrangement resists tension in specific directions
- Classes: Hyaline, Elastic, Fibrocartilage
