Human Development: From Conception to Infancy
Cephalocaudal and Proximodistal Principles
Cephalocaudal principle
Head to tail
Development proceeds from the head to the trunk.
Proximodistal principle
Near to far
Development proceeds from the center of the body out.
Prenatal Development Stages
GERMINAL STAGE
Fertilization to 2 weeks
Zygote divides, becomes more complex
Moves through fallopian tube to uterus
Now a blastocyst
Implants into uterine wall around 6th day
Three layers of cells cluster:
- Ectoderm
Skin, nails, hair, teeth, sensory organs, nervous system - Endoderm
Digestive
Fungal Infections: Types, Symptoms, and Causes
Superficial Fungal Infections
- Above the skin (cosmetic infections).
- No pathological problems.
- Example 1: Pityriasis Versicolor (paño blanco): A fungus that reproduces over the skin surface, changing the skin pigment. It is most noticeable when exposed to sunlight. It can cause dandruff (caspa). Fungus species: Malassezia furfur.
- Example 2: Tineas: Black to white spots on the body (foot: plantaris, hands: palmaris). Fungus species: Hortaea werneckii.
- Example 3: White and Black Piedra: Nodules in the
Nervous and Endocrine Systems: Functions and Components
The Neuron: Signal Transmission
Neurons receive and transmit signals via nerve impulses. These impulses travel along the neuron’s plasma membrane in one direction. The process begins at the dendrites with electrical waves, continues through the neuron, and reaches the axon. The synapse, a buffer zone between the axon’s terminal branches, facilitates signal transmission using chemical neurotransmitters.
Brain Structure and Function
Brain: The outermost layer, the cerebral cortex, exhibits gray folds
Egg Preservation Methods and Quality Assessment
Egg Alterations Caused by Microorganisms
- White rot: Caused by coliforms and Micrococcus.
- Red putrefaction: Caused by Pseudomonas.
- Green putrefaction: Caused by a Bacillus that produces pyocyanin.
- Black rot: Caused by melanogenic Proteus.
- Mold growth on the shell: Following the existing humidity in the storage premises, mottled greenish spots of a more or less mucous consistency arise.
- Fungus growth inside the egg: In the area of the colonies, the clear is greenish if the contaminant is Aspergillus, blue
Sex Determination, Genetic Disorders, and DNA Processes
Sex Determination
The mechanism of sex determination has always been a puzzle for geneticists. The initial clue about the genetic or chromosomal mechanism of sex determination can be traced back to some experiments carried out in insects. In fact, the cytological observations made in a number of insects led to the development of the concept of a genetic or chromosomal basis of sex determination.
Mutation
Mutation is a phenomenon that results in the alteration of DNA sequences and, consequently, results
Read MoreBiochemistry Essentials: Key Concepts and Q&A
Biochemistry: Key Concepts and Q&A
Metabolic Pathways and Cellular Respiration
- Which of the following metabolic pathways does *not* happen inside the mitochondria? Acetyl-CoA production
- Which of the following elements increase the activity of the pyruvate dehydrogenase complex (PDH)? All of them
- The flow rate through the Krebs cycle is controlled by: All of them
- Indicate the true statement about the respiratory chain and oxidative phosphorylation: In eukaryotes, oxidative phosphorylation occurs in