bio 2nd sem 1st grading

• Integumentary System


  The largest organ system in the human body, consisting of the skin and its associated structures (hair, nails, and glands)
• Human Integument or Skin or Cutaneous Membrane

  The external covering of the body, acting as a protective layer that shields the internal organs and tissues from the external environment
• Some animals use their skin for regulation of body temperature, sensation, excretion, respiration, and secretion
• Some animals find the skin to provide a clue as to their sex, while skin secretions allow some animals to attract or repel other animals
• Components of Human Integument

  • Epidermis
  • Dermis
• Epidermis

  The outermost layer of the skin, primarily composed of epithelial cells (stratified squamous epithelium), preventing water loss and resisting abrasion
• Dermis


  The layer beneath the epidermis, composed of connective tissue containing fibroblasts, blood vessels, nerves, hair follicles, and sweat glands; known as the "true skin"
• Keratinization


  The process by which cells in the epidermis produce a protein called keratin, making the skin tough and resistant
• Strata


  The different layers of the epidermis
• Layers of the Epidermis

  1. Stratum Corneum

  2. Stratum Lucidum

  3. Stratum Granulosum

  4. Stratum Spinosum

  5. Stratum Germinativum or Stratum Basale
• Callus

  Thickened and toughened skin usually caused by friction or pressure
• Corn


  A type of callus with a hard, cone-shaped core, often found on the toes
• Skin Color


  The result of melanin, blood flow, and thickness of the stratum corneum
• Melanin


  A pigment that gives color to the skin, hair, and eyes, providing protection against UV light from the sun
• Melanocytes


  Cells in the skin that produce melanin
• Melanosomes


  Structures within melanocytes that contain melanin and transport it to the surrounding skin cells
• Heavy Pigmentation


  Refers to a higher concentration of melanin in the skin
• Melanin Production


  Regulated by melanocytes in response to environmental stimuli, influenced by genetic factors, sun exposure, and hormonal changes
• Cleavage or Tension Lines of the Dermis


  Represent the natural alignment of collagen fibers in the dermis, considered by surgeons when making incisions to minimize scarring
• Skin Incision


  A cut made through the skin
• Striae

  Also known as stretch marks, linear marks resulting from rapid stretching of the skin (e.g., abdomen and breasts of women during pregnancy)
• Accessory Skin Structures

  • Hair
  • Smooth Musc
• Striae, also known as stretch marks, are linear marks resulting from rapid stretching of the skin. Example: Abdomen and breasts of women during pregnancy
• Accessory Skin Structures

  • Hair
  • Smooth muscles called arrector pili
  • Glands
  • Nails
• Hair


  A filamentous structure emerging from hair follicles, made of keratin. It serves various functions, including insulation and sensory perception. Most abundant accessory
• General Parts of the Hair

  • Shaft
  • Cuticle
  • Cortex
  • Medulla
  • Root
• Cuticle

  The outermost layer of the hair shaft, forming a protective covering. A single layer of overlapping cells that holds the hair in the hair follicle
• Cortex


  The middle layer of the hair shaft, sandwiched between the outer cuticle and the inner medulla. It contains the bulk of the hair's protein, mainly keratin, and determines the hair's strength, elasticity, and color. Covered by the cuticle
• Medulla


  The innermost layer of the hair shaft, consisting of soft and loosely packed cells. Surrounded by the cortex
• Hair Follicle is a structure within the skin that surrounds the root of the hair
• In humans, some hair is found everywhere in the skin except: Palms, Soles, Lips, Nipples, Parts of the genitalia, The distal segments of the fingers and toes
• Generation of Hairs

  • Lanugo
  • Vellus
  • Terminal
• Lanugo refers to fine, soft, and downy hairs that cover the body of a developing fetus. These hairs typically appear on the skin during the second trimester of pregnancy
• Vellus are the soft, short, and fine hairs that cover most of the body surface, excluding certain areas
• Terminal hairs are longer and darker hairs that grow in specific areas of the body during and after puberty. The growth is influenced by hormonal changes, particularly the increase in androgens (male hormones) during puberty
• Hair-Growth Cycle

  1. Anagen

  2. Catagen

  3. Telogen

  4. Return to Anagen
• Eyelashes grow for about 30 days and rest for 105 days; scalp hairs grow for 3 years and rest for 1-2 years
• Pattern Baldness is the most common cause of hair loss and typically follows a predictable pattern. It is often hereditary and can affect
• Hair growth cycle

  Beginning of a new hair growth cycle marks
• Eyelashes growth cycle


  Grow for about 30 days and rest for 105 days