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Lecture Notes: Connective, Muscle, Cartilage, and Nervous Tissue Vocabulary

Blood (General connective tissue)

  • Blood is a fluid connective tissue composed of plasma (the liquid portion with soluble proteins and molecules) and formed elements (cells and platelets).
  • Formed elements include red blood cells (RBCs), white blood cells (WBCs), and platelets.
  • Red blood cells are also called erythrocytes.
  • White blood cells are often referred to by specific types (e.g., lymphocytes); platelets are also called thrombocytes.
  • RBCs lack internal organelles and nuclei; they are biconcave, which makes the membranes come close in the center and allows light to pass through when aligned on their side.
  • WBCs contain nuclei and may have granules depending on the cell type; slides may show different morphologies.
  • The slide examples emphasize recognizing RBCs, WBCs, and platelets, and recognizing that a given slide could be asking for a tissue-type identification (blood is a connective tissue) or a specific cell type.
  • Key terminology and synonyms:
    • Erythrocyte = red blood cell
    • Lymphocyte = a type of white blood cell
    • Thrombocyte = platelet
  • Practical note: In exams, read the question carefully to determine whether you should identify the tissue type (blood) or a specific cell type (e.g., erythrocyte, lymphocyte, thrombocyte).

Bone (Compact bone)

  • Compact bone features osteons (Haversian systems).
  • Each osteon has concentric lamellae around a central canal called the Haversian (or central) canal where vessels, nerves, and sometimes other structures run.
  • Lacunae are small spaces within the lamellae that house osteocytes (bone cells).
  • Osteocytes maintain the bone matrix and participate in repair; they reside in lacunae.
  • The central canal and surrounding lamellae form a tree-like, layered structure that resembles growth rings.
  • Medical note: Bone remodeling occurs throughout life; the transcript mentions remodeling roughly every 10–15 years, reflecting ongoing turnover and rebuilding of compact bone. This can be expressed as: ext{Bone remodeling cycle} \approx 10 ext{ to } 15 ext{ years}
  • Mesenchyme: Mentioned as the origin of all connective tissues; not the focus of a quiz in this particular lecture.

Loose connective tissue

  • Adipose tissue (fat): easy to recognize due to large lipid droplets that push the nucleus to the periphery, creating a characteristic ring-like appearance.
    • Function: insulation, energy storage, cushioning (e.g., fat capsules around kidneys).
  • Areolar connective tissue: loose network with loose fibers and cells; fibroblasts produce fibers; fibers include collagen (CF) and thinner fibers.
    • Appears as a loose, open matrix with scattered cells and fibers.
  • Reticular connective tissue: has dark reticular fibers forming a mesh-like network; fibroblasts support the matrix.
    • The provided image may be less clear, but reticular fibers are dark and prominent in this tissue.

Dense connective tissue

  • Dense irregular connective tissue: fibers are arranged in multiple directions (swirled pattern).
    • Location example: dermis, where tissue must withstand stresses from many directions.
    • Purpose: provides strength and flexibility in various orientations; fibers are thick and the tissue is relatively less open.
  • Dense regular connective tissue: collagen fibers are aligned in a single direction.
    • Function: can stretch in one direction and recoil (elasticity, though the primary property is oriented strength).
    • Examples: tendons and ligaments; helps joints and movement in a preferred direction (e.g., knee ligaments).
  • Note on misidentification: dense connective tissue can resemble smooth muscle in some slides; look for the presence or absence of striations and intercalated discs to distinguish muscle from dense connective tissue.

Cartilage (connective tissue)

  • Elastic cartilage: dense elastic fibers within the matrix; highly flexible.
    • Typical locations: structures requiring flexibility with support (e.g., epiglottis, external ear).
    • Key feature: abundant elastic fibers visible in the matrix.
  • Fibrocartilage: very dense, with thick collagen fibers; high resistance to compression.
    • Typical locations: intervertebral discs, pubic symphysis.
    • Characteristic: cells (chondrocytes) reside in lacunae scattered among dense matrix.
  • Hyaline cartilage: the most common type; glassy matrix with relatively fine collagen.
    • Typical locations: trachea (to maintain airway openness), articular surfaces.
    • Features: large lacunae with chondrocytes; evenly distributed matrix; perichondrium may be present depending on location.
  • Trachea cross-section (illustrative slide):
    • Epithelium with cilia on the luminal surface.
    • Submucosa and lamina propria as connective tissue layers supporting the epithelium.
    • Hyaline cartilage C-shaped rings providing open airway; perichondrium externally.
    • This composition maintains airway patency and supports respiration.
  • Quick reminder: cartilage types are determined by matrix composition and fiber content, and each type has a distinct functional role in the body.

Muscle tissue

  • Three types of muscle tissue:
    • Skeletal muscle: striated, voluntary, typically multinucleated; has visible striations due to myofibrils and sarcomeres.
    • Cardiac muscle: striated; contains intercalated discs that connect cells and support synchronized contraction; typically one nucleus per cell, though some cells can be binucleated; mitochondrial density is high.
    • Smooth muscle: non-striated; spindle-shaped cells with a single central nucleus; arranged in sheets; present in walls of hollow organs and vessels; capable of slow, sustained contractions; lacks striations.
  • Striations and intercalated discs as diagnostic features:
    • Striations indicate skeletal or cardiac muscle; absence suggests smooth muscle.
    • Intercalated discs indicate cardiac muscle; they are the junctions where adjacent cardiac cells connect and communicate.
  • Functional notes:
    • Skeletal muscle fibers are multinucleated and show multiple nuclei along the fiber.
    • Cardiac tissue contains syncytia-like properties where cardiac cells contract in a coordinated fashion due to gap junctions at intercalated discs.
    • Smooth muscle exhibits non-striated appearance and organized sheets; contraction can be coordinated or slow, depending on the tissue and stimulus.
  • Example observation: cross-sections may show arteries/veins with tunica layers; smooth muscle is often concentrated in the tunica media, contributing to vessel constriction and dilation.

Nervous tissue

  • Two cell types: neurons and glial (support) cells.
  • Neurons: large cell bodies with nucleus, dendrites, and axons; primary cells for transmitting signals.
  • Glial cells: support cells that provide nutrients, insulation, and maintenance for neurons.
  • Neuromuscular junction: a synapse where a nerve fiber interfaces with a muscle fiber.
    • At the junction, acetylcholine is released from vesicles into the synaptic cleft.
    • Muscle fibers have a high density of acetylcholine receptors under the nerve terminal; binding opens gated channels and triggers contraction.
    • There are numerous neuromuscular junctions to enable fine motor control and graded force; more active recruitment of motor units increases the contraction strength.
  • Visual cues in slides: neuromuscular junctions are highlighted; the presence of synapses and acetylcholine receptors is a key diagnostic feature for identifying nervous tissue interaction with muscle.

Integumentary system – models and lab preparation

  • Lab focus: exercise 6 and 7 deals with integumentary system; no lab practical questions explicitly from integumentary questions, but physiology-related questions may appear in lectures.
  • Models and PAL (point-and-label) guides help you identify hair follicles, glands, subcutaneous tissue, tactile receptors, and associated structures.
  • Hair follicle and glands: study labels on the models to recognize hair shaft, follicle structure, sebaceous glands, sweat glands, etc.
  • Tactile structures: Meissner’s corpuscles and Pacinian corpuscles (tactile receptors) contribute to pressure, heat, and touch sensation; linked to subcutaneous and dermal layers.
  • Skin model resources: a new model is available; both the skin model and the new model include accompanying video tutorials recorded by Dr. Schmidt.
  • Exam and study aids for integumentary system:
    • A dedicated PAL for label practice; use model labels to reinforce structure recognition.
    • Unit 8 contains lab-practical study resources and two study- session lectures not recorded; a review will be provided before the practical.
    • PDF answers: contains longer, recap-style responses for the practical questions; VisioX extended answers accompany the PDFs.
    • Color versus black-and-white images: black-and-white images (e.g., figures 87 and 88) are easier to study for tissue types; color images provide anatomical context and body-location references.

Additional notes and study tips

  • Mesenchyme: all tissues originate from mesenchymal cells; this concept is foundational but not a focus of this particular quiz.
  • When identifying slides, consider context beyond color; look for landmarks such as:
    • Blood: presence of plasma vs formed elements; presence of osteons vs lamellae for bone; matrix density for cartilage.
    • Cartilage: lacunae with chondrocytes, perichondrium presence, and the type of cartilage determined by fiber content.
    • Bone: osteocytes in lacunae, concentric lamellae, and Haversian canals; circular organization reminiscent of tree rings.
    • Muscle tissue: striations and intercalated discs help differentiate skeletal and cardiac; absence indicates smooth muscle.
    • Nervous tissue: neuron cell bodies with dendrites/axons; glial cells provide support.
  • Real-world context: understanding tissue structure helps explain organ function (e.g., blood transport in arteries, structural support in bone, elasticity in the aorta, and coordinated contraction in cardiac muscle).
  • Ethical/philosophical/practical implications: recognizing tissue structure informs medical diagnoses, surgical planning, and understanding how aging affects tissue elasticity, remodeling, and regenerative capacity. Also, practical implications include preserving model integrity and using the correct labels during lab measurements and exams.

Quick connections to foundational principles

  • Structure determines function: tissue architecture (e.g., striations, lacunae, intercalated discs) directly relates to how tissues contract, conduct signals, or withstand mechanical stress.
  • Tissue origin and differentiation: mesenchyme origin underpins the development of connective tissues and their diverse forms (bone, cartilage, adipose, dense/loose tissues).
  • Systems integration: skin and integumentary structures interact with nervous and vascular systems to sense, respond, and regulate homeostasis (e.g., tactile receptors, vascular smooth muscle control).

Exam-oriented reminders

  • Expect questions asking to identify tissue type from a slide (blood, bone, cartilage, adipose, areolar, dense irregular, dense regular, elastic cartilage, fibrocartilage, hyaline cartilage, skeletal muscle, cardiac muscle, smooth muscle, nervous tissue).
  • Be prepared to distinguish between similar-looking tissues (e.g., dense regular vs smooth muscle) by looking for key features (striations and intercalated discs, vs lack of striations and elongated nuclei).
  • For muscle: know the differences between skeletal, cardiac, and smooth in terms of striations, nuclei, and cell junctions (intercalated discs).
  • For cartilage: memorize the three main types (hyaline, fibrocartilage, elastic) and their typical locations and properties.
  • For bone: remember osteon structure (central canal, lamellae, lacunae, osteocytes) and the concept of remodeling.
  • For integumentary references: use PALs and skin models to reinforce the anatomy of hair follicles, glands, and tactile receptors; review Meissner’s and Pacinian corpuscles and their relevance to sensation.